Question 1

Excessive use of which type of fertiliser is mainly responsible for the presence of toxic levels of nitrates in groundwater, leading to problems such as blue baby syndrome?

Accepted Answer

Introduction / Context: Groundwater quality can be adversely affected by agricultural practices. When fertilisers are applied in large quantities, nutrients can leach down through the soil and contaminate underground water. One well known issue is nitrate contamination, which can cause health problems such as methemoglobinemia or blue baby syndrome in infants. This question asks which type of fertiliser, when used excessively, is primarily responsible for toxic nitrate levels in groundwater. Given Data / Assumptions: • The focus is on toxic substances in groundwater related to fertiliser overuse. • Options include nitrogenous, phosphate, and potassium fertilisers, singly or in combination. • We assume typical agricultural conditions where fertilisers are applied to fields and some portion may leach downward with water movement. Concept / Approach: Nitrogenous fertilisers provide nitrogen in forms such as nitrate (NO3-) or ammonium (NH4+), which plants need for growth. Examples include urea, ammonium nitrate, and ammonium sulphate. Nitrate is highly soluble in water and does not bind strongly to soil particles, so it can easily leach into groundwater if applied in excessive amounts or if irrigation and rainfall are high. High nitrate levels in drinking water are associated with blue baby syndrome, where nitrate is converted to nitrite in the body, interfering with haemoglobin ability to carry oxygen in infants. In contrast, phosphate ions tend to bind strongly to soil particles and usually do not leach as easily; they are more associated with surface water eutrophication when eroded soil enters rivers and lakes. Potassium fertilisers also tend to be adsorbed by soil particles and are less prone to deep leaching than nitrates. Therefore, nitrogenous fertilisers are primarily responsible for nitrate contamination of groundwater when overused. Step-by-Step Solution: Step 1: Recall that nitrogenous fertilisers supply nitrogen in forms like nitrate and ammonium, which are used by plants for protein and chlorophyll synthesis. Step 2: Understand that nitrate is very soluble and can move with percolating water through the soil profile down to groundwater. Step 3: Recognise that overapplication of nitrogenous fertilisers, or their use just before heavy rains, greatly increases the risk of nitrate leaching. Step 4: Compare this with phosphate fertilisers; phosphates often bind to soil minerals and generally pose a greater risk for surface water eutrophication than for deep groundwater contamination. Step 5: Consider potassium fertilisers; potassium ions can be held on soil exchange sites and, although some leaching may occur, they are not commonly associated with toxic groundwater contamination in the same way as nitrates. Step 6: Conclude that nitrogenous fertilisers are the main source of nitrate pollution in groundwater when used excessively. Verification / Alternative check: Environmental health reports and soil science references frequently cite nitrate contamination of groundwater as a major issue in areas of intensive agriculture. They link high nitrate levels to overuse of nitrogenous fertilisers and poor management of animal wastes. Drinking water standards normally specify maximum permissible nitrate concentrations, and public health guidelines explain the connection between nitrate rich water and blue baby syndrome in infants. These documents do not identify phosphate or potassium fertilisers as primary culprits for toxic groundwater contamination, reinforcing that nitrogenous fertilisers are the main concern. Why Other Options Are Wrong: Phosphate fertilisers only are wrong because phosphates generally bind to soil particles and do not leach as readily into deep groundwater; they are more important for surface water eutrophication than for nitrate toxicity in groundwater. Potassium fertilisers only are incorrect because potassium ions are not typically associated with severe groundwater toxicity in the same way as nitrates; they can leach but usually do not cause the same health problems. Phosphate and potassium fertilisers together are also wrong because combining them does not create the specific nitrate contamination that causes blue baby syndrome; nitrogen is missing from this pair. Common Pitfalls: Students may assume that any fertiliser can contaminate groundwater and may pick an option that lists multiple nutrients. Another mistake is not remembering which nutrient is specifically associated with blue baby syndrome. To answer correctly, keep in mind that nitrate contamination of groundwater is mainly linked to overuse of nitrogenous fertilisers, not phosphate or potassium fertilisers. Final Answer: Thus, excessive use of fertilisers that primarily contaminate groundwater with toxic nitrates involves nitrogenous fertilisers that supply nitrate or ammonium to crops.

Question 2

With reference to earthquakes, which of the following statements are correct? A. Earthquakes largely occur along converging plate boundaries only. B. The point of origin of an earthquake within the lithosphere is called the focus or hypocentre. C. T…

Accepted Answer

Introduction / Context: Understanding earthquakes is an important part of geography and earth science. Questions often test knowledge of where earthquakes occur, how they originate, and how their effects vary with distance. This question presents four statements about plate boundaries, the focus (hypocentre), epicentre, and the pattern of intensity, and asks you to determine which ones are correct. It requires careful reading and conceptual clarity, because some statements may be only partly correct or exaggerated. Given Data / Assumptions: • Statement A claims that earthquakes largely occur along converging plate boundaries only. • Statement B defines the focus or hypocentre as the point of origin of an earthquake within the lithosphere. • Statement C says that intensity decreases with distance from the epicentre. • Statement D claims that epicentres always lie on continents only. • The task is to select the option that includes all and only the correct statements. Concept / Approach: Statement B is a standard textbook definition: the focus (or hypocentre) is the point inside the Earth where the rupture starts and seismic energy is first released. Directly above this point, on the surface, lies the epicentre. Statement C is broadly correct in practice: as seismic waves travel outward from the epicentre, they spread out and lose energy, so the observed intensity of shaking generally decreases with increasing distance, although local conditions can modify this pattern. Statement A is problematic because it says earthquakes largely occur along converging plate boundaries only, ignoring divergent and transform plate boundaries where many earthquakes also occur, such as along mid ocean ridges and the San Andreas Fault. Thus, A is not acceptable as correct. Statement D is clearly false because many epicentres are located beneath the oceans along mid ocean ridges and oceanic trenches. Therefore, only B and C are correct, corresponding to option C in the code choices. Step-by-Step Solution: Step 1: Evaluate statement B: by definition, the focus or hypocentre is the point inside the Earth where the earthquake originates. This is correct. Step 2: Evaluate statement C: seismic intensity, as felt at the surface, tends to decrease with increasing distance from the epicentre because energy spreads out and is absorbed by the Earth. This general statement is correct, even though local geology can cause variations. Step 3: Examine statement A: while many strong earthquakes do occur at convergent plate boundaries (subduction zones and collision zones), significant earthquakes also occur along divergent boundaries (mid ocean ridges) and transform boundaries (such as the San Andreas Fault). Saying largely occur along converging plate boundaries only is misleading and incomplete, so we treat it as incorrect. Step 4: Examine statement D: the epicentre is the surface projection of the focus and can lie anywhere on the Earth surface, including under oceans. Many major quakes, such as those along oceanic trenches and mid ocean ridges, have epicentres under the sea. Therefore, the claim that epicentres always remain over continents is false. Step 5: Combine the findings: B and C are correct; A and D are incorrect. Step 6: Identify the option that lists B and C only, which is option C in the answer choices. Verification / Alternative check: Plate tectonics theory shows seismic belts not only at convergent boundaries but also along mid ocean ridges (divergent) and major transform faults, confirming that earthquakes are not confined to convergent boundaries. Seismology texts define the focus (hypocentre) and epicentre exactly as described in B and in the explanation above. Intensity maps of earthquakes (isoseismal maps) typically show the highest intensities near the epicentre with decreasing values outward, although site effects can cause local anomalies, supporting the general validity of statement C. Records of large submarine earthquakes that generate tsunamis clearly show epicentres in oceanic regions, directly contradicting statement D. These lines of evidence confirm that only B and C are correct. Why Other Options Are Wrong: A and B only is wrong because A is not acceptable; earthquakes are also frequent along divergent and transform plate boundaries, not just converging boundaries. A, B and C is incorrect because it includes statement A, which is misleading as it restricts major seismicity to converging plate boundaries only. A and D is clearly wrong because both statements A and D are incorrect; D ignores oceanic epicentres altogether. Common Pitfalls: Students may be tempted to accept A because many powerful earthquakes occur at convergent boundaries, particularly in subduction zones, and they may not think about divergent and transform boundaries. Another common pitfall is to ignore oceanic earthquakes, focusing only on damaging events on land, which leads to accepting D. To answer correctly, remember that earthquakes occur along all types of plate boundaries, the focus is the origin point inside the Earth, intensity generally decreases with distance from the epicentre, and epicentres can lie under both continents and oceans. Thus, B and C only is the correct combination. Final Answer: Therefore, the correct statements are B and C only, corresponding to option C.

Question 3

At high altitudes, mountaineers and travellers may suffer from altitude sickness. This condition is mainly caused by which of the following?

Accepted Answer

Introduction / Context: Altitude sickness, also called acute mountain sickness, is a common problem for people who travel rapidly to high mountains without proper acclimatisation. Symptoms include headache, nausea, dizziness, and fatigue. This question tests your understanding of the basic physiological cause of altitude sickness, which involves changes in the partial pressure of gases in the atmosphere, particularly oxygen. Given Data / Assumptions: • The context is high altitudes, such as mountains above a few thousand metres. • Options mention high or low partial pressures of oxygen and carbon dioxide, and low haemoglobin levels. • We assume a person who has ascended relatively quickly from low altitude to high altitude, without long term adaptation. Concept / Approach: Atmospheric pressure decreases with altitude. While the percentage of oxygen in the air remains approximately constant at about 21 percent, the total atmospheric pressure is lower at high altitude, so the partial pressure of oxygen (the portion of total pressure contributed by oxygen) is also lower. This reduced partial pressure of oxygen means that less oxygen diffuses from the lungs into the blood with each breath, leading to tissue hypoxia. The body attempts to compensate by increasing breathing and heart rate, but if ascent is too rapid, symptoms of altitude sickness develop. Haemoglobin levels are not initially low; in fact, over time, the body produces more red blood cells to adapt. The partial pressure of carbon dioxide is usually lower at high altitude because increased breathing (hyperventilation) blows off more carbon dioxide. Therefore, the main cause of altitude sickness is low partial pressure of oxygen, not high oxygen, low haemoglobin, or high carbon dioxide. Step-by-Step Solution: Step 1: Recall that atmospheric pressure decreases with height above sea level, reducing the pressure of all gases, including oxygen. Step 2: Recognise that at a given altitude, the fraction of oxygen remains similar, but the partial pressure of oxygen (PO2) falls because total pressure is lower. Step 3: Understand that the lower PO2 in the air leads to a smaller gradient for oxygen diffusion from alveoli into the blood, causing less oxygen to enter the bloodstream. Step 4: Note that tissues then receive less oxygen, causing symptoms such as headache, nausea, and fatigue, typical of altitude sickness. Step 5: Evaluate the other options: high partial pressure of oxygen is opposite to reality; haemoglobin levels do not suddenly drop upon ascent; high carbon dioxide partial pressure is also unlikely because increased breathing drives CO2 levels down. Step 6: Conclude that low partial pressure of oxygen at high altitude is the correct cause of altitude sickness. Verification / Alternative check: Physiology textbooks link acute mountain sickness to hypobaric hypoxia, which means low oxygen pressure due to reduced barometric pressure. They explain that acclimatisation involves increased ventilation, increased red blood cell production, and other adaptations to improve oxygen delivery. Medical advice for high altitude travel emphasises gradual ascent and sometimes prophylactic medications to reduce the risk of altitude sickness, all of which are measures to cope with low oxygen availability, not with high oxygen or carbon dioxide. This evidence confirms that low partial pressure of oxygen is the main factor responsible for altitude sickness. Why Other Options Are Wrong: High partial pressure of oxygen at high altitude is wrong because atmospheric and oxygen partial pressures both decrease with altitude, not increase. Low level of haemoglobin in all high altitude residents is incorrect; people who live at high altitude often have higher haemoglobin levels as an adaptation, and visitors do not suddenly lose haemoglobin when they ascend. High partial pressure of carbon dioxide at high altitude is also wrong because hyperventilation at altitude tends to lower carbon dioxide levels, not raise them. Common Pitfalls: Students sometimes confuse oxygen concentration with partial pressure and may think that because oxygen is always about 21 percent of the air, it should not cause problems. The key is that the partial pressure (absolute pressure) of oxygen matters for gas exchange, not just its percentage. Another pitfall is to mix up altitude sickness with anaemia, which also reduces oxygen carrying capacity but has a different cause. To avoid these errors, remember that altitude sickness is fundamentally due to low partial pressure of oxygen at high altitudes, causing inadequate oxygenation of body tissues. Final Answer: Therefore, altitude sickness at high altitude is mainly caused by low partial pressure of oxygen.

Question 4

In terms of mass percentage, which sequence correctly represents the major elemental composition of an average adult human body?

Accepted Answer

Introduction / Context: The human body is made up mainly of a few key elements, and understanding their relative proportions is important in biology and biochemistry. While there are many trace elements, four major elements dominate body mass: oxygen, carbon, hydrogen, and nitrogen. This question asks you to identify the correct order of these elements by mass percentage in an average adult human body. Given Data / Assumptions: • The elements considered are oxygen (O), carbon (C), hydrogen (H), and nitrogen (N). • The options provide different possible sequences of these four elements in decreasing order of mass percentage. • We assume an average healthy adult with typical body composition, acknowledging that exact percentages can vary slightly among individuals. Concept / Approach: Approximate mass percentages of the major elements in the human body are often given as: oxygen about 60 to 65 percent, carbon about 18 percent, hydrogen about 9 to 10 percent, and nitrogen about 3 percent. From these values, it is clear that oxygen is the most abundant element by mass, largely because water makes up a large fraction of body weight and water contains oxygen. Carbon is second because it forms the backbone of organic molecules such as proteins, carbohydrates, and lipids. Hydrogen is third, present in both water and organic compounds, and nitrogen is fourth, mainly found in amino acids and nucleic acids. Therefore, the correct descending order by mass is O > C > H > N. Step-by-Step Solution: Step 1: Recall that the human body is about 60 to 70 percent water by mass, and each water molecule contains one oxygen and two hydrogen atoms, contributing significantly to oxygen content by mass. Step 2: Recognise that oxygen therefore becomes the most abundant element by mass in the body. Step 3: Consider carbon next; all organic molecules in the body, including carbohydrates, lipids, proteins, and nucleic acids, are built on carbon skeletons, making carbon the second most abundant element. Step 4: Note that hydrogen is abundant in both water and organic molecules but, because it is much lighter than oxygen and carbon, its total mass contribution is lower than that of oxygen and carbon. Step 5: Understand that nitrogen is an essential component of amino acids and nucleotides, but it is present in smaller amounts, making it fourth in terms of mass percentage. Step 6: From this reasoning, derive the order O > C > H > N and select option A as correct. Verification / Alternative check: Biology texts that discuss chemical composition of the human body typically present tables or charts showing element percentages. These consistently show oxygen as the most abundant element by mass, followed by carbon, then hydrogen, and finally nitrogen among the four major elements. While specific percentages vary slightly depending on the source, the order remains the same. This robust agreement across references confirms that O > C > H > N is the correct sequence by mass percentage for an average adult human body. Why Other Options Are Wrong: C > O > H > N is wrong because it places carbon above oxygen; in reality, oxygen is more abundant due to the high water content of the body. O > H > C > N is incorrect because it places hydrogen above carbon; although hydrogen atoms are numerous, their low mass means that the total mass of hydrogen is less than that of carbon. N > C > O > H is clearly wrong because nitrogen is the least abundant of the four by mass, not the most abundant. Common Pitfalls: Students sometimes think that carbon must be the most abundant because life is called carbon based. Another pitfall is to focus on the number of atoms rather than their mass; hydrogen has many atoms but each atom is very light. To avoid these mistakes, remember that water dominates body mass and water contains a lot of oxygen, making oxygen come first. Thus, the correct descending order of major elements by mass in an average adult human body is O > C > H > N. Final Answer: Therefore, the correct sequence for the major elemental composition of the adult human body by mass is O > C > H > N.

Question 5

Which of the following statements about the vertical temperature structure of the Earth atmosphere are correct? 1. In the stratosphere, temperature increases with altitude. 2. In the mesosphere, temperature decreases with altitude. 3. The lowest tem…

Accepted Answer

Introduction / Context: The atmosphere is divided into several layers based on temperature trends with height: troposphere, stratosphere, mesosphere, and thermosphere. Understanding how temperature changes in each layer is fundamental in climatology and physical geography. This question presents four statements about the temperature structure and asks you to identify which ones are correct. It requires a clear mental picture of the vertical temperature profile of the atmosphere. Given Data / Assumptions: • Statement 1: In the stratosphere, temperature increases with altitude. • Statement 2: In the mesosphere, temperature decreases with altitude. • Statement 3: The lowest temperature of the atmosphere is recorded in the upper mesosphere. • Statement 4: Tropopause is approximately an isothermal zone (temperature is nearly constant with height). • The task is to select the combination of statements that correctly describes real atmospheric behaviour. Concept / Approach: In the troposphere, the lowest layer of the atmosphere, temperature generally decreases with altitude at an average environmental lapse rate, because the surface is the main source of heating by absorbing solar energy and re radiating infrared. Near the top of the troposphere lies the tropopause, where temperature becomes nearly constant with height, so it is often described as an isothermal layer or zone. Above the tropopause, in the stratosphere, temperature increases with height because of absorption of ultraviolet radiation by ozone, creating a temperature inversion. Above the stratosphere is the mesosphere, in which temperature again decreases with altitude, reaching very low values at the mesopause, which separates the mesosphere from the thermosphere. The mesopause is typically the coldest region of the atmosphere. Therefore, statements 1, 2, 3, and 4 are all correct. Step-by-Step Solution: Step 1: Consider the stratosphere. Ozone absorbs ultraviolet radiation, heating the upper parts of this layer. As a result, temperature increases with altitude in the stratosphere, confirming statement 1 as correct. Step 2: Examine the mesosphere, which lies above the stratopause. There is little ozone and less absorption of solar radiation, so temperature once again decreases with height, making statement 2 correct. Step 3: Recall that the mesopause, located at the top of the mesosphere, is the region of minimum temperature in the atmosphere, often reaching very low values. Therefore, statement 3, which says that the lowest temperature is recorded in the upper part of the mesosphere, is also correct. Step 4: Think about the tropopause, the boundary between troposphere and stratosphere. At this level, the temperature lapse rate typically becomes nearly zero, and temperature remains almost constant with height over a certain depth, which justifies calling it approximately an isothermal zone. Thus, statement 4 is correct. Step 5: Since all four statements are correct, the option that includes 1, 2, 3, and 4 together is option D. Verification / Alternative check: Standard atmospheric science diagrams of temperature versus height show a decrease in temperature through the troposphere, a near constant temperature at the tropopause, an increase through the stratosphere, a decrease again through the mesosphere, and then a rapid increase in the thermosphere. They also label the mesopause as the coldest region of the atmosphere. Climatology textbooks use similar descriptions, emphasising the temperature inversion in the stratosphere and the approximate isothermal character of the tropopause. These sources confirm each of the four statements, supporting the choice of all four as correct. Why Other Options Are Wrong: 1 and 2 only is wrong because it excludes statements 3 and 4, both of which are correct according to the known vertical temperature profile. 1, 2 and 3 only is incorrect because it omits statement 4, which correctly describes the tropopause as an approximately isothermal zone. 3 and 4 only is wrong because it leaves out statements 1 and 2, which are also correct about the stratosphere and mesosphere. Common Pitfalls: Students often remember that temperature decreases with height in the troposphere but may not recall the inversions and changes in higher layers. Some may be unsure about the tropopause being nearly isothermal or may misplace the coldest region. To avoid confusion, it is helpful to memorise the typical temperature pattern: troposphere (decrease), tropopause (almost constant), stratosphere (increase), mesosphere (decrease, with coldest temperatures at the mesopause). With this pattern in mind, it becomes clear that all four statements in the question are correct. Final Answer: Therefore, the correct choice is that all four statements 1, 2, 3 and 4 are correct, corresponding to option D.

Question 6

Which one of the following statements about syzygy and related eclipse conditions in the Sun–Earth–Moon system is NOT correct?

Accepted Answer

Introduction / Context: Syzygy is an important concept in astronomy and celestial mechanics, referring to special alignments of celestial bodies. In the context of the Earth–Moon–Sun system, syzygy is closely associated with New Moon, Full Moon, and eclipse conditions. This question provides four statements about syzygy and asks which one is not correct, so you must evaluate each statement carefully based on what you know about lunar phases and eclipses. Given Data / Assumptions: • Syzygy refers to an approximate straight line alignment of three celestial bodies, often the Sun, Earth and Moon. • Conjunction refers to a New Moon syzygy, with the Moon near the Sun as seen from Earth. • Opposition refers to a Full Moon syzygy, with the Moon opposite the Sun in the sky. • Perihelion is the point in Earth orbit when it is closest to the Sun and occurs once per year. Concept / Approach: In the Sun–Earth–Moon system, syzygy occurs when the three bodies are nearly in a straight line. At New Moon, the Moon is between Earth and Sun; at Full Moon, Earth is between Sun and Moon. Eclipses are special cases of syzygy where the alignment passes close to the orbital nodes. Solar eclipses occur at New Moon when the Moon’s shadow falls on the Earth, and lunar eclipses occur at Full Moon when the Earth’s shadow falls on the Moon. Statements A, B, and C are consistent with these definitions: syzygy is the nearly straight line alignment; syzygy at conjunction can lead to a solar eclipse; syzygy at opposition can lead to a lunar eclipse if the alignment is favourable. Statement D incorrectly restricts syzygy conjunction to Earth perihelion only. In reality, New Moon syzygies occur approximately once every lunar month, independent of Earth perihelion. Perihelion is not a requirement for syzygy or eclipses. Therefore, statement D is not correct. Step-by-Step Solution: Step 1: Evaluate statement A. Syzygy is indeed used to describe an approximate straight line configuration of three bodies, such as Sun, Earth and Moon, with an angle near 180 degrees. This statement is correct. Step 2: Evaluate statement B. At New Moon, the Moon is in conjunction with the Sun as seen from Earth, and when this syzygy occurs near a node of the Moon orbit, a solar eclipse can take place. This statement is correct. Step 3: Evaluate statement C. At Full Moon, the Moon is opposite the Sun, and when this syzygy occurs near a node, the Earth’s shadow can fall on the Moon, producing a lunar eclipse. This statement is also correct. Step 4: Evaluate statement D. It claims that syzygy conjunction occurs only at perihelion, the point in Earth orbit when it is closest to the Sun. However, New Moon syzygies happen every lunar month (approximately every 29.5 days) regardless of whether Earth is at perihelion or not. Perihelion happens just once a year and is unrelated to the regular occurrence of syzygies. Therefore, statement D is not correct. Step 5: Since the question asks for the statement that is NOT correct, choose statement D. Verification / Alternative check: Lunar phase calendars show that New Moon (conjunction) and Full Moon (opposition) occur roughly every 29.5 days. Eclipses occur only when these phases coincide with the Moon being near one of its nodes. Astronomical data shows that Earth perihelion occurs once per year in early January and does not control the monthly pattern of syzygies. Textbooks describing eclipses and syzygy do not tie conjugation syzygy exclusively to perihelion. These facts confirm that statements A, B, and C conform to standard definitions and that statement D incorrectly restricts syzygy conjunction to perihelion. Why Other Options Are Wrong (i.e., actually correct statements): The alignment of the Sun, Earth and Moon in a nearly straight line of about 180 degrees is called syzygy is a correct definition of syzygy in the context of the Earth–Moon–Sun system. Syzygy conjunction (New Moon in line with the Sun) can cause a solar eclipse when the alignment is near a node is correct because solar eclipses occur at New Moon syzygy when geometric conditions are satisfied. Syzygy opposition (Full Moon opposite the Sun) can cause a lunar eclipse when the alignment passes near a node is correct because lunar eclipses occur at Full Moon syzygy when the Earth lies between the Sun and Moon. Common Pitfalls: Students may be unfamiliar with the term syzygy and may focus on eclipse details, or they may find the mention of perihelion in statement D attractive because it sounds technical. Another pitfall is forgetting that New Moons and Full Moons occur monthly, not just once a year. To avoid confusion, remember that syzygy refers to alignments during New Moon and Full Moon, which happen regularly, while perihelion is a separate orbital event that does not control syzygy. Therefore, statement D is the incorrect one. Final Answer: The statement that is NOT correct is “Syzygy conjunction occurs only at the time of Earth perihelion around the Sun and not at other times.”

Question 7

Which one of the following landforms is NOT primarily associated with wind erosion processes in arid and semi-arid regions?

Accepted Answer

Introduction / Context: Geomorphology studies different landforms and the agents that create them, such as running water, wind, ice, and waves. In desert and semi-arid regions, wind is a major agent of erosion, transportation, and deposition, producing characteristic features. This question asks you to identify which listed landform is not primarily related to wind erosion, so you must recall which terms belong to aeolian (wind) processes and which belong to other geomorphic agents. Given Data / Assumptions: • The landforms listed are wind gap, zeugen, dreikanter, and demoiselle. • We assume standard definitions used in physical geography texts. • The focus is on whether the dominant erosional agent is wind or another process such as running water. Concept / Approach: Zeugen are elongated rock ridges with flat tops and steep sides formed by wind abrasion and deflation acting on horizontally bedded rocks in deserts. Dreikanter are ventifacts, usually pebbles or small boulders that have been abraded on three faces by wind driven sand, giving them a characteristic three faced shape. Demoiselles or rock pedestals often appear as mushroom like forms where wind abrasion erodes softer material near the base more than the harder cap rock, and although water and other processes may contribute, they are commonly listed among wind erosion features in deserts. In contrast, a wind gap is a pass in a mountain ridge through which a river once flowed but which is now dry; it is associated with river capture and fluvial erosion rather than with wind erosion. The term wind in wind gap refers to the fact that only wind now passes through the gap, not to wind having carved it originally. Therefore, wind gap is not a landform produced primarily by wind erosion. Step-by-Step Solution: Step 1: Recall that zeugen are sculpted by wind abrasion acting on layered rocks, leaving resistant caps and eroded sides, making them classic aeolian landforms. Step 2: Remember that dreikanter are individual stones shaped by wind blown sand, with three distinct abraded faces, clearly formed by wind. Step 3: Recognise that demoiselles or rock pedestals can form where wind erosion removes softer material near the base of a rock column, leaving a narrow pedestal supporting a harder cap, and are generally taught as features of wind erosion. Step 4: Consider wind gap: it is a mountain pass that was formerly occupied by a river before river capture diverted the flow elsewhere. The gap is a residual valley cut by running water, not by wind. Step 5: Conclude that while zeugen, dreikanter, and demoiselles are associated with wind erosion, wind gap is not; it is a fluvial landform now left dry. Verification / Alternative check: Physical geography textbooks classify landforms based on the dominant erosional agent. Under wind erosion, they commonly list features such as yardangs, zeugen, rock pedestals (demoiselles), ventifacts including dreikanter, and deflation hollows. Under fluvial erosion and river capture, they discuss wind gaps and water gaps, explaining that wind gaps are former river valleys now abandoned by the stream, usually due to stream piracy. These classifications confirm that wind gap belongs to the category of river related landforms, whereas zeugen, dreikanter, and demoiselles are associated with wind action in arid regions. Why Other Options Are Wrong: Zeugen is wrong as the answer because it is a recognised aeolian landform produced by wind erosion acting on layered rocks. Dreikanter (ventifact with three wind-abraded faces) is incorrect because it is a classic example of a rock shaped by wind driven sand in deserts. Demoiselle (mushroom-like rock pedestal in desert areas) is also wrong because such forms are typically listed among wind erosion features, where wind abrasion plays a major role in undercutting the base. Common Pitfalls: Students may be misled by the term wind gap and assume that wind created the landform, when in fact it was originally formed by running water. The word wind here refers to the present condition (only wind passes through) rather than the formative process. Another pitfall is not remembering the names of less common aeolian features such as zeugen or dreikanter. To avoid these mistakes, focus on the dominant erosional agent: wind gaps are relic valley passes formed by rivers, while zeugen, dreikanter, and demoiselles are associated with wind erosion. Final Answer: Thus, the landform that is NOT primarily related to wind erosion is the wind gap.

Question 8

Very small insoluble particles suspended in a liquid can best be separated from the liquid by which of the following methods?

Accepted Answer

Introduction / Context: In school level chemistry and laboratory practice, you learn various methods of separating mixtures: filtration, decantation, crystallisation, distillation, and centrifugation. The choice of method depends on the properties of the mixture, such as particle size and solubility. This question asks which method is most suitable for separating very small insoluble particles from a liquid, where simple methods like decantation or filtration may not be effective on their own. Given Data / Assumptions: • The particles are insoluble but very small and suspended in a liquid (a suspension or colloid like mixture). • The options include crystallisation, fractional distillation, centrifugation, and decantation. • We assume no special filters are available that can easily trap very fine particles by ordinary gravity filtration. Concept / Approach: Centrifugation involves spinning a mixture at high speed so that denser particles experience a strong outward force, causing them to move toward the bottom of the container and form a sediment or pellet. The clear liquid (supernatant) can then be poured off. This method is particularly useful for separating very small insoluble particles that might remain suspended for a long time or pass through ordinary filter paper. Crystallisation is used to separate dissolved solids from a solution by forming crystals; it is not appropriate for insoluble particles already present. Fractional distillation is used for separating liquids with different boiling points, not for removing solid particles from a liquid. Decantation involves gently pouring off the clear liquid from a settled solid, but it is effective mainly when particles are large enough to settle quickly by gravity; for very fine particles, settling may be too slow or incomplete. Therefore, centrifugation is the best choice here. Step-by-Step Solution: Step 1: Recognise that the mixture is a liquid with very small insoluble particles; they do not dissolve but are small enough to settle very slowly or remain suspended. Step 2: Recall that centrifugation increases the effective gravitational force on the particles by spinning the sample, causing even fine particles to move outward and settle more rapidly. Step 3: Compare this with decantation, which relies on natural settling under gravity; it is slow and often incomplete when particles are very small. Step 4: Understand that crystallisation is designed to recover dissolved solutes by forming crystals, not to remove insoluble suspended particles. Step 5: Notice that fractional distillation separates components based on different boiling points, usually for liquid mixtures, not for solids suspended in liquids. Step 6: Conclude that centrifugation is the most suitable method for separating very small insoluble particles from a liquid. Verification / Alternative check: Laboratory protocols for separating blood cells from plasma, or for clarifying suspensions such as milk or bacterial cultures, routinely use centrifuges. These examples involve very small particles (cells, fat globules, or bacteria) that do not settle quickly by gravity alone. Educational materials on separation of mixtures describe centrifugation as the method of choice for suspensions where the solid particles are too fine for easy filtration or rapid settling. These real world uses confirm that centrifugation is the correct answer for this type of problem. Why Other Options Are Wrong: Crystallisation is wrong because it is used to recover dissolved solids from a solution by forming crystals, not to separate undissolved fine particles already present as a suspension. Fractional distillation is incorrect because it separates liquid mixtures based on boiling point differences, not solid particles from liquids. Decantation is also wrong in this context because it depends on particles settling by gravity, which is inefficient for very small particles that remain suspended for long periods. Common Pitfalls: Students may confuse crystallisation with general solid liquid separation or may think of decantation as a solution for all solid suspensions without considering particle size. Another pitfall is not distinguishing between separating dissolved substances and separating suspended solids. To avoid these errors, remember that centrifugation is specifically designed to separate very small insoluble particles from liquids by applying high rotational force, making it the correct choice here. Final Answer: Therefore, the best method to separate very small insoluble particles from a liquid is centrifugation.

Question 9

Marble, which is widely used as a building and sculptural stone, belongs to which category of rocks?

Accepted Answer

Introduction / Context: Rocks are classified into three major groups based on their origin: igneous, sedimentary, and metamorphic. Marble is a well known rock used in buildings, monuments, and sculptures. This question tests whether you can correctly identify the rock category to which marble belongs, based on how it forms in nature. Given Data / Assumptions: • The options are sedimentary, igneous, metamorphic, or none of these. • Marble is known to be derived from another rock type by transformation under heat and pressure. • Basic understanding of rock formation processes is assumed. Concept / Approach: Sedimentary rocks form by the deposition and lithification of sediments, such as sandstones and limestones. Igneous rocks form by solidification of molten magma or lava, such as granite and basalt. Metamorphic rocks form when existing rocks are transformed under heat, pressure, and chemically active fluids, without melting into magma. Marble is formed when limestone (a sedimentary rock composed mainly of calcite) is subjected to high temperatures and pressures, typically during regional metamorphism or contact metamorphism. The calcite grains recrystallise, producing a dense, crystalline rock called marble. This clearly places marble in the metamorphic rock category, not sedimentary or igneous. Step-by-Step Solution: Step 1: Recall that limestone is a sedimentary rock formed mainly from the accumulation of shells and skeletal fragments composed of calcium carbonate. Step 2: Understand that when limestone is buried and subjected to high temperatures and pressures, its minerals recrystallise into a new texture and structure without melting. Step 3: Recognise that this process of solid state transformation is called metamorphism, and the product rock is called marble. Step 4: Compare this process with igneous rock formation, which involves complete melting and solidification; marble does not form this way. Step 5: Note that marble is not a sedimentary rock itself, even though it originates from a sedimentary parent; the metamorphic process changes its classification. Step 6: Conclude that marble is a metamorphic rock. Verification / Alternative check: Geology textbooks categorise common metamorphic rocks and list marble as a typical non foliated metamorphic rock derived from limestone or dolostone. They describe marble as consisting of interlocking calcite crystals and often mention its use in art and architecture. In contrast, lists of sedimentary rocks include limestone and sandstone, and lists of igneous rocks include granite and basalt, not marble. This consistent classification confirms that marble belongs to the metamorphic category. Why Other Options Are Wrong: Sedimentary rock is wrong because marble is produced by metamorphism of sedimentary limestone; the original rock is sedimentary, but after transformation it becomes metamorphic. Igneous rock is incorrect because marble does not form from cooling magma or lava; there is no complete melting step in its formation. None of these categories is wrong because marble clearly fits into the metamorphic category, so the option suggesting none is not appropriate. Common Pitfalls: Students sometimes confuse marble with limestone because they share similar chemical composition (mainly calcium carbonate). Another pitfall is forgetting that metamorphic rocks are named after their parent rocks in many cases, but are not the same rock type. To avoid confusion, remember that limestone is sedimentary, while its metamorphosed product marble is a metamorphic rock. This distinction helps in many geology questions. Final Answer: Therefore, marble is classified as a metamorphic rock.

Question 10

In physics of road design, the phenomenon of raising the outer edge of a curved road above the inner edge to provide the necessary centripetal force for safe turning of vehicles is called:

Accepted Answer

Introduction / Context: When vehicles move along a curved path, they require a centripetal force to keep them on the curve and prevent skidding outward or inward. Road engineers design curves so that part of this centripetal force comes from the normal reaction of the road surface, not only from friction. This is achieved by raising the outer edge of the road above the inner edge. The question asks for the standard term used in physics and road engineering for this design feature. Given Data / Assumptions: • The situation is a vehicle taking a turn on a curved road. • The outer edge of the road is raised relative to the inner edge, creating an inclined surface. • The options include terms such as banking, cornering, elevation, and tempering of roads. Concept / Approach: When a vehicle moves around a curve, it needs a centripetal force directed toward the centre of curvature. On a flat road, this force must be supplied entirely by the lateral friction between the tyres and the road. If the required centripetal force exceeds what friction can provide, the vehicle may skid. To reduce reliance on friction and improve safety, roads are often built with a slope or tilt, such that the surface is inclined at an angle to the horizontal. The outward edge is raised, and the inward edge is lower. This arrangement is called banking of roads. The normal reaction of the road on the vehicle then has a component toward the centre of curvature, providing part of the centripetal force. Terms like cornering and elevation are more general descriptive words and are not used as the specific technical term in this context. Tempering relates to heat treatment in materials and is not relevant to road geometry. Step-by-Step Solution: Step 1: Recall that centripetal force is needed for circular motion and must be directed toward the centre of the curve. Step 2: Recognise that on a level road, friction between tyres and road provides this force, which may be insufficient at high speeds or on slippery surfaces. Step 3: Understand that by tilting the road surface so that the outer edge is higher, the normal reaction from the road has a horizontal component that helps provide centripetal force. Step 4: Note that this tilting or sloping of the road at curves is specifically termed banking of roads in physics and engineering. Step 5: Evaluate other options: cornering is a general term for turning corners; elevation is a generic term for height; tempering is a metal heat treatment process. Step 6: Conclude that banking of roads is the appropriate term describing the phenomenon in the question. Verification / Alternative check: Physics textbooks dealing with circular motion of vehicles devote a section to banked curves and derive expressions for the optimum banking angle at which a vehicle can negotiate a curve without relying on friction. They explicitly call this practice banking of roads. Engineering manuals on highway design talk about superelevation, which is the practical implementation of banking in road construction, again emphasising that the outer edge of the pavement is raised to counteract the outward tendency of vehicles. No standard reference uses cornering of roads or tempering of roads as technical names for this phenomenon. Why Other Options Are Wrong: Cornering of roads is wrong because it is not a technical term describing the raised edge design; it simply refers to turning at a corner. Elevation of roads is incorrect as a specific term here; while roads do have an elevation above sea level, this does not describe the tilting of the road surface on curves to provide centripetal force. Tempering of roads is clearly wrong because tempering is a metallurgical process used to treat metals, not a road design feature. Common Pitfalls: Students may confuse the common English word elevation with the technical concept of banking or may assume that any term mentioning a turn, such as cornering, is appropriate. Another pitfall is not connecting the physical concept of centripetal force to the specific engineering practice used to provide it. To answer correctly, remember that raising the outer edge of a curved road to help provide centripetal force is known as banking of roads. Final Answer: Hence, the phenomenon described is called banking of roads.

Question 11

In astronomy, which one of the following stars listed in the options is the nearest star to the Earth (ignoring the Sun itself)?

Accepted Answer

Introduction / Context: The question asks about the nearest star to the Earth among the listed options, ignoring the Sun. This is a classic general science and astronomy multiple choice question that helps learners remember basic facts about stars in our local stellar neighbourhood and distinguish between bright stars in the sky and stars that are actually closest in terms of distance from the Earth. Given Data / Assumptions: The Sun is not considered, even though it is the closest star to the Earth. The options given are Sirius, Arcturus, Spica, and Proxima Centauri. We assume standard accepted astronomical distances measured in light years. Concept / Approach: To answer this question, we need to recall or understand which stars are relatively close to the solar system. Some stars are very bright in the night sky because they are luminous, not necessarily because they are close. Others may not appear as bright but are physically much nearer to us. The concept of a light year, which is the distance light travels in one year, is used to compare how far away these stars are from the Earth and the Sun. We simply compare approximate distances of each of the listed stars from the solar system. Step-by-Step Solution: Step 1: Recall that Sirius is about 8.6 light years away from the Sun and is one of the brightest stars in the night sky. Step 2: Remember that Arcturus is roughly 36 to 37 light years away from the Earth, so it is significantly farther than Sirius. Step 3: Spica is even more distant, at more than 200 light years away, so it cannot be the nearest star among the options. Step 4: Proxima Centauri is part of the Alpha Centauri star system and is located at a distance of about 4.24 light years from the Sun, making it the closest known star to the solar system other than the Sun. Step 5: Compare the distances: Proxima Centauri at about 4.24 light years is closer than Sirius, Arcturus, and Spica, so it is the correct answer among the given options. Verification / Alternative check: A good verification method is to recall the standard fact taught in basic astronomy that Proxima Centauri is the closest known star to the Sun beyond the Sun itself. Many textbooks explicitly state that Proxima Centauri is the nearest star to the Earth after the Sun. By cross-checking common distances, we see that all other stars listed are farther away in terms of light years, so this confirms that Proxima Centauri is correctly identified as the nearest among the options provided. Why Other Options Are Wrong: Sirius: Although very bright in the night sky, Sirius is about 8.6 light years away, which is farther than Proxima Centauri. Arcturus: Arcturus is much farther, around mid-thirties in light years from the Earth, so it cannot be the closest. Spica: Spica is more than 200 light years away, making it very distant compared to Proxima Centauri. Common Pitfalls: A common mistake is to assume that the brightest star in the night sky must be the closest star. Brightness depends on both intrinsic luminosity and distance. Very luminous stars can appear bright even if they are far away, while nearby stars can be faint if they are intrinsically less luminous. Learners may also forget that the Sun, although the closest star, is not considered here because the question clearly focuses on the options listed. Confusing visual brightness with physical proximity is the key misconception that needs to be avoided. Final Answer: The nearest star to the Earth among the given options (ignoring the Sun) is Proxima Centauri.

Question 12

Within our solar system, which of the following planets has the least mass compared to the others listed in the options?

Accepted Answer

Introduction / Context: This question tests basic knowledge of the planets in the solar system, specifically focusing on their relative masses. Understanding which planet has the least mass is important for general science and astronomy because mass affects gravity, atmosphere, and many other planetary characteristics. The learner needs to compare common planets and identify which one is physically the smallest in terms of mass among the listed options. Given Data / Assumptions: The planets listed are Neptune, Jupiter, Mars, and Mercury. We consider their actual physical masses, not their volumes or distances from the Sun. Standard accepted planetary mass values from astronomy are assumed. Concept / Approach: The approach is to recall or look up the approximate masses of the listed planets. Jupiter and Neptune are both gas giants, whereas Mars and Mercury are smaller rocky planets. Generally, gas giants are far more massive than terrestrial planets. Among terrestrial planets, Mercury is known to be the smallest in both size and mass. The concept of comparing planetary properties such as size, mass, and composition is central to understanding this question. Step-by-Step Solution: Step 1: Recall that Jupiter is the largest and most massive planet in the solar system. Therefore, it cannot be the planet with the least mass. Step 2: Neptune is also a gas giant and is much more massive than any of the terrestrial planets, so it is not the correct answer. Step 3: Compare Mars and Mercury. Mars is larger than Mercury in diameter and has greater mass, though both are rocky planets. Step 4: Mercury is known as the smallest planet in the solar system in terms of both radius and mass after the reclassification of Pluto as a dwarf planet. Step 5: Therefore, among Neptune, Jupiter, Mars, and Mercury, the planet with the least mass is Mercury. Verification / Alternative check: To verify, consider approximate mass values. Jupiter has a mass more than 300 times that of the Earth. Neptune has a mass around 17 times the mass of the Earth. Mars has about one tenth of the Earth's mass. Mercury has even less mass than Mars, less than half of Mars mass, and is recognized as the smallest planet. This quick sanity check confirms that Mercury has the least mass of all planets listed in the options. Why Other Options Are Wrong: Neptune: A gas giant and very massive compared to terrestrial planets, so it is far from being the least massive. Jupiter: The most massive planet in the solar system, making it the exact opposite of what the question asks for. Mars: Smaller and less massive than Earth, but still larger and more massive than Mercury. Common Pitfalls: Learners sometimes confuse the order of planets by distance from the Sun with their sizes or masses. Another common error is mixing up Mars and Mercury because both are relatively small terrestrial planets. Some may also incorrectly recall Pluto as a planet and think about it as the smallest, but Pluto is now officially classified as a dwarf planet. Remembering that Mercury is the smallest and least massive of the eight major planets is crucial for avoiding these mistakes. Final Answer: The planet in the solar system with the least mass among the given options is Mercury.

Question 13

Which one of the following States of India is not covered by Flood Forecasting Stations that have been set up by the Central Water Commission (CWC)?

Accepted Answer

Introduction / Context: This question belongs to Indian geography and environmental management. It focuses on the distribution of Flood Forecasting Stations established by the Central Water Commission (CWC). Such stations are vital for flood prediction, issuing timely warnings, and reducing damage to life and property. The task is to identify which state among the options is not covered by this specific network of flood forecasting stations. Given Data / Assumptions: The question explicitly refers to Flood Forecasting Stations, not food forecasting, so a minor wording correction is assumed based on standard usage. The options are Rajasthan, Jammu and Kashmir, Tripura, and Himachal Pradesh. We assume the typical examination reference data used in competitive exams where this question appears. Concept / Approach: The Central Water Commission sets up flood forecasting stations mainly in river basins that are flood prone and require continuous monitoring. Many plains states with large rivers, such as those around the Ganga and Brahmaputra basins, have extensive networks. To solve this question, we recall which states are explicitly mentioned in standard exam references as being covered by CWC flood forecasting networks and identify the one state that was traditionally excluded in that list. This is more of a factual recall question than a calculation or reasoning question. Step-by-Step Solution: Step 1: Recall that Rajasthan, although largely arid, does have interstate rivers and has been mentioned in descriptions of CWC flood forecasting coverage. Step 2: Jammu and Kashmir have important rivers like Jhelum, Chenab, and other Himalayan rivers, making flood forecasting necessary, so it appears in the list of states covered. Step 3: Tripura is in the north eastern region with many rivers and heavy monsoon rains, and it also appears in the standard list of states covered by flood forecasting stations. Step 4: Himachal Pradesh, despite being a Himalayan state, is identified in typical exam explanations as not being covered by CWC flood forecasting stations in the original scheme that this question refers to. Step 5: Therefore, among the states listed, Himachal Pradesh is the one that is not covered by the flood forecasting stations in the context of this examination question. Verification / Alternative check: A way to verify is to cross check with standard geography and environment preparation material and previous year solutions where the same question appears. These sources explicitly mention that Rajasthan, Jammu and Kashmir, and Tripura are all included among states covered by CWC flood forecasting stations, while Himachal Pradesh is not included in that particular scheme reference. This alignment across multiple exam key explanations confirms Himachal Pradesh as the accepted correct answer for this question context. Why Other Options Are Wrong: Rajasthan: Mentioned as one of the states covered by CWC flood forecasting, despite being relatively dry compared to river plains states. Jammu and Kashmir: This region has important rivers and flood vulnerability, and it is listed among covered states. Tripura: A north eastern state with high rainfall and rivers, which is included in the coverage for flood forecasts. Common Pitfalls: Many learners are tempted to select Rajasthan or Tripura because they either think arid regions do not need flood stations or they assume smaller north eastern states are sometimes ignored. Another common confusion is between Himalayan states such as Himachal Pradesh and Jammu and Kashmir, since both have mountain rivers. It is important to remember that this question reflects a specific officially referenced list used in competitive exams, not necessarily the current or future situation, and in that list Himachal Pradesh is the state that is not covered by CWC flood forecasting stations. Final Answer: The state that is not covered by Flood Forecasting Stations set up by the Central Water Commission is Himachal Pradesh.

Question 14

When hot water is poured into an empty water bottle and the bottle keeps its shape without softening, the plastic of the bottle is most likely which type of material?

Accepted Answer

Introduction / Context: This question tests basic knowledge of materials science and polymers, especially how different plastics behave when heated. Common plastic items like bottles are made from various polymer types, and their reaction to heat depends on whether they are thermoplastics or thermosetting plastics. The scenario describes a water bottle that does not soften even when hot water is added, and we must identify the correct category of plastic that explains this behaviour. Given Data / Assumptions: Hot water is placed in an empty bottle, so the plastic is exposed to elevated temperature from the inside. The bottle keeps its shape and does not soften or deform. The options given include thermoplastic, PVC, polyurethane, and thermosetting. We assume that the hot water temperature is high enough to soften thermoplastics if they are near or above their softening point. Concept / Approach: Plastics are broadly classified into thermoplastics and thermosetting plastics. Thermoplastics soften on heating and can be remoulded multiple times. Thermosetting plastics, once set by heat or chemical reaction, do not soften again on heating; instead, they tend to retain their shape or may char at very high temperatures. To answer the question, we must recall that a material which maintains its structural rigidity when exposed to heat is characteristic of a thermosetting plastic rather than a typical thermoplastic. Step-by-Step Solution: Step 1: Understand that thermoplastics such as polyethylene and polyethylene terephthalate soften gradually when heated close to their softening or glass transition temperatures. Step 2: Realise that if the bottle were made of a thermoplastic, very hot water might cause some softening or deformation, especially if the plastic is thin. Step 3: Recall the definition of thermosetting plastics. These plastics cross link during curing and form a rigid three dimensional structure that does not soften upon reheating. Step 4: The question states that the bottle keeps its shape and does not soften, which is consistent with the behaviour of thermosetting plastics. Step 5: Among the given options, thermosetting is the correct general category that matches this behaviour better than the other specific materials listed. Verification / Alternative check: As a conceptual check, one can recall everyday examples. Thermoplastic items like disposable water bottles often deform with very hot liquids, whereas thermosetting plastics such as those used in some electrical fittings or cookware handles remain rigid at higher temperatures. Although in real life many commercial water bottles are made from thermoplastics designed to withstand moderate heat, the typical textbook style reasoning for a material that does not soften under hot water favours the thermosetting category. This consistency between theory and the described behaviour supports the chosen answer. Why Other Options Are Wrong: Thermoplastic: By definition, this type softens when heated sufficiently, so it is not the best match for a bottle that does not soften with hot water. PVC: Polyvinyl chloride is a thermoplastic polymer. It can soften or deform under the action of heat, especially in thin sections. Polyurethane: Polyurethane can appear in many forms, but the option is not as precise as the general classification of thermosetting plastics requested in the question. Common Pitfalls: Learners sometimes confuse real world commercial products with ideal textbook examples. In actual practice, some thick or specially formulated thermoplastics may withstand hot water without obvious deformation. However, exam questions usually rely on simple definitions: thermoplastics soften on heating, while thermosetting plastics remain rigid. Another common error is to focus on brand names or particular polymers rather than the broad behaviour based classification that the question is targeting. Final Answer: The water bottle that does not soften when hot water is added is best described as being made from a thermosetting plastic.

Question 15

In environmental science, the term Green House Effect refers to which of the following processes related to the Earth atmosphere?

Accepted Answer

Introduction / Context: The Green House Effect is a fundamental concept in environmental science and climate studies. This question checks whether the learner understands the correct meaning of the term and can distinguish it from other unrelated phenomena, such as ozone layer protection or local pollution. Understanding the Green House Effect is essential for grasping issues like global warming, climate change, and energy balance on the Earth surface and in the atmosphere. Given Data / Assumptions: The term to be defined is Green House Effect. The options include explanations related to tropical house pollution, ozone layer function, trapping of solar energy, and damage to green buildings. We assume standard textbook definitions used in environmental science. Concept / Approach: The Green House Effect refers to the process by which certain gases in the Earth atmosphere trap heat. Incoming solar radiation reaches the Earth surface, which then emits infrared radiation back towards space. Greenhouse gases such as carbon dioxide, methane, and water vapour absorb and re-radiate some of this heat, causing warming near the surface and lower atmosphere. The approach is to recall this definition and then choose the option that clearly describes this trapping of energy rather than unrelated ideas like ultraviolet blocking or local pollution. Step-by-Step Solution: Step 1: Recall that the Green House Effect is named by analogy with a greenhouse, where glass allows sunlight in but slows the escape of heat, leading to a warmer interior. Step 2: Understand that in the Earth atmosphere, gases such as carbon dioxide, methane, nitrous oxide, and water vapour play the role of greenhouse gases. Step 3: Identify that the main idea is trapping of outgoing infrared radiation, which leads to an increase in the temperature of the lower atmosphere and surface. Step 4: Examine the options and recognise that option C, which mentions trapping of solar energy due to atmospheric gases, best describes this effect in simple exam language. Step 5: Confirm that the other options refer to different phenomena, such as ozone layer protection from ultraviolet radiation or local pollution, and therefore do not match the definition of the Green House Effect. Verification / Alternative check: You can verify the meaning by remembering that discussion about global warming and climate change almost always refers to the Green House Effect. In those contexts, greenhouse gases are said to trap heat and enhance the natural Green House Effect, leading to higher average global temperatures. No standard environmental science textbook uses the term to refer to house pollution or paint damage, confirming that trapping of energy by atmospheric gases is the correct explanation. Why Other Options Are Wrong: Pollution in houses in tropical region: This describes indoor pollution and has no relation to the global atmospheric Green House Effect. Prevention of ultraviolet radiation by the ozone layer: This refers to the protective role of the ozone layer, not the Green House Effect. Damage to green painted buildings: This is not a recognised scientific process and is unrelated to climate science. Common Pitfalls: A frequent confusion is between ozone layer depletion and the Green House Effect. Some learners mix up the role of ozone, which mainly protects from ultraviolet radiation, with greenhouse gases, which trap infrared radiation and cause warming. Another mistake is to interpret the term too literally as something related to green coloured houses or buildings. To avoid these pitfalls, always connect the Green House Effect to heat trapping, greenhouse gases, and global temperature rise. Final Answer: The Green House Effect is best described as the trapping of solar energy by atmospheric gases leading to warming of the Earth.

Question 16

Karst topography: Statement I says that by far the most common topographic landform in a Karst terrain is the sinkhole, and Statement II says that topographically a sinkhole is a depression that can vary in depth from less than a metre to a few hund…

Accepted Answer

Introduction / Context: This question examines understanding of Karst topography, which develops in regions of soluble rocks such as limestone. The focus is on sinkholes, which are characteristic features of Karst landscapes. The learner needs to interpret two given statements about sinkholes and decide whether both are correct and whether the second statement properly explains the first. This is a conceptual geography and geomorphology question involving logical reasoning about related statements. Given Data / Assumptions: Statement I: By far the most common topographic form in a Karst terrain is the sinkhole. Statement II: Topographically, a sinkhole is a depression that varies in depth from less than a metre to a few hundred metres. A Karst terrain is an area where dissolution of soluble rocks creates distinctive surface and subsurface features. Concept / Approach: Karst landscapes are characterised by features such as sinkholes, dolines, caves, and disappearing streams. Among these, sinkholes (also called dolines) are widespread and numerous. They appear as shallow or deep depressions in the ground formed by dissolution or collapse of underlying rock. To answer the question, we need to check the factual correctness of each statement and then determine whether Statement II explains why sinkholes are the most common landform in Karst terrain as expressed in Statement I. Step-by-Step Solution: Step 1: Evaluate Statement I. Standard physical geography texts describe sinkholes as the most common and diagnostic surface form in Karst regions. Therefore, Statement I is true. Step 2: Evaluate Statement II. A sinkhole is defined as a rounded depression of various depths, which can be less than a metre deep or extend hundreds of metres, depending on geological conditions and the degree of collapse or dissolution. Therefore, Statement II is also true. Step 3: Consider whether Statement II explains Statement I. The description in Statement II shows that sinkholes are common surface depressions of varying size and depth in Karst regions, which fits with the idea that these features dominate the topography. Step 4: Because sinkholes form extensively wherever soluble rock is present and water can percolate, they naturally become the most abundant topographic form in Karst landscapes, so the detailed description in Statement II supports and clarifies the claim in Statement I. Step 5: Therefore, both statements are true, and Statement II is the correct explanation of Statement I. Verification / Alternative check: A further check can be made by recalling that Karst regions are often mapped by counting sinkholes, as they are numerous and easy to identify on aerial photographs and topographic maps. Such regions may have hundreds or thousands of sinkholes. The depth variation, from shallow depressions to deep pits, is indeed a well documented aspect of sinkhole morphology. This consistency with textbook descriptions confirms that the statements are factually correct and that the detailed definition in Statement II helps explain the general statement in Statement I. Why Other Options Are Wrong: Both true but Statement II is not the correct explanation: This is incorrect because the morphology and depth range described in Statement II directly relate to why sinkholes dominate Karst topography. Statement I true, Statement II false: Statement II is factually correct, so this pairing is wrong. Statement I false, Statement II true: Statement I is not false; sinkholes are indeed recognised as the most common Karst surface landform. Common Pitfalls: Learners may confuse Karst features such as caves, underground streams, and sinkholes, sometimes thinking that caves are the most common form because they are dramatic. However, caves are often hidden below ground, while sinkholes cover large surface areas and are more numerous. Another mistake is to focus only on the depth description in Statement II and overlook how it supports the idea that sinkholes are widespread and varied, which is precisely what underlies Statement I. Remember that in assertion reason type questions, you must check both truth and the explanatory relationship. Final Answer: Both statements are individually true, and Statement II is the correct explanation of Statement I.

Question 17

River geomorphology: Statement I says that incised meanders are formed in the mature stage of a river, while Statement II says that incised meanders are characterised by rejuvenation and upliftment of the land. What is the correct relationship betwe…

Accepted Answer

Introduction / Context: This question assesses understanding of fluvial landforms, specifically incised meanders. It uses an assertion and reason format with two statements about when incised meanders form and what they indicate. The learner must evaluate the truth of each statement and determine whether one explains the other. Knowledge of river stages, rejuvenation, and vertical erosion is needed to answer correctly. Given Data / Assumptions: Statement I: Incised meanders are formed in the mature stage of a river. Statement II: Incised meanders are characterised by rejuvenation and upliftment of land. We assume the standard three stage model of river development: youthful, mature, and old stages. Concept / Approach: Meanders are sinuous bends in a river, commonly associated with the mature stage when lateral erosion and deposition dominate. Incised meanders, however, are meanders that have been cut deeply into the landscape due to renewed vertical erosion. This renewed erosion usually occurs when the river is rejuvenated, either because of uplift of the land or a drop in base level (such as sea level fall). The key is to distinguish ordinary meanders of the mature stage from incised meanders that reflect rejuvenation rather than simple maturity. Step-by-Step Solution: Step 1: Consider Statement I. It claims incised meanders are formed in the mature stage. While meanders commonly occur in the mature stage, incised meanders specifically are associated with renewed downcutting, not simply the normal mature stage conditions. Step 2: Because incised meanders form when a previously established meandering river gains renewed energy to erode vertically, they are more correctly linked to rejuvenation rather than the ordinary mature stage. Therefore, Statement I is false as stated. Step 3: Evaluate Statement II. Rejuvenation occurs when there is uplift of the land or a fall in base level, increasing the river gradient and enhancing vertical erosion. Step 4: This increased vertical erosion cuts deeply into the existing meander pattern, producing incised meanders that often appear as steep walled meandering valleys. Step 5: Therefore, Statement II is true, since incised meanders are indeed characteristic of rejuvenation and upliftment of land. Verification / Alternative check: Textbooks on geomorphology often provide diagrams of meanders in different stages. Ordinary meanders with wide floodplains are associated with the mature stage. When rejuvenation occurs, the river entrenches itself into its previous floodplain, yielding incised or entrenched meanders. Some sources use specific examples like the Colorado River or other rejuvenated rivers to illustrate such features. These references confirm that incised meanders are tied to rejuvenation rather than solely to the mature stage described in Statement I. Why Other Options Are Wrong: Both true and Statement II explains Statement I: This would require Statement I to be correct, which it is not, because it misplaces incised meanders strictly in the mature stage without mentioning rejuvenation. Both true but Statement II not explanation: Again, this assumes Statement I is true, which is incorrect. Statement I true, Statement II false: This reverses the actual situation. Statement II accurately describes the rejuvenation context of incised meanders. Common Pitfalls: The main pitfall is confusing ordinary meanders with incised meanders. Students often remember that meanders belong to the mature stage and then apply that fact incorrectly to incised meanders. Another error is to ignore the role of rejuvenation and land uplift, assuming that any deeply cut valley is simply youthful. Remember that incised meanders require a preexisting meandering pattern plus renewed downcutting, which is directly linked to rejuvenation processes. Final Answer: Statement I is false but Statement II is true, so the correct option is Statement I is false but Statement II is true.

Question 18

Glacial landforms: Statement I says that portions of glacial troughs may show remarkably flat valley floors, and Statement II says that this flat floor in a glacial trough is produced by uniform glacial erosion. What is the correct relationship betw…

Accepted Answer

Introduction / Context: This question focuses on glacial geomorphology, particularly on glacial troughs, which are U shaped valleys carved by moving ice. Two statements are given about flat valley floors in these troughs and their origin. The learner must decide whether each statement is true and whether the second statement explains the first. Understanding how glaciers erode rock and shape valleys is key to solving this item. Given Data / Assumptions: Statement I: Portions of glacial troughs may exhibit remarkably flat floors. Statement II: The flat floor in a glacial trough is produced by uniform glacial erosion. We assume standard descriptions of U shaped valleys and glacial erosion processes from physical geography. Concept / Approach: Glaciers are powerful agents of erosion. As they move, they abrade bedrock and pluck blocks from valley sides and floors. Over time, this action transforms a former V shaped river valley into a U shaped glacial trough with steep sides and a relatively flat or gently sloping floor. The concept of uniform glacial erosion along the valley floor explains the creation of that flatness. The approach is to assess whether each statement reflects this mainstream understanding. Step-by-Step Solution: Step 1: Evaluate Statement I. Glacial troughs, such as those in formerly glaciated mountain regions, commonly show flat or broad floors. This is a central characteristic used to distinguish them from V shaped river valleys, so Statement I is true. Step 2: Examine Statement II. Uniform glacial erosion along the valley floor, including abrasion and plucking, tends to remove irregularities and deepen and widen the valley, producing a smoother, flatter bottom over long periods. Step 3: Because the glacier occupies much of the valley cross section, erosion acts widely rather than being confined to a narrow channel, which contributes to the flatness of the trough floor described in Statement I. Step 4: Therefore, Statement II describes the process that leads to the landform property mentioned in Statement I. Step 5: Both statements are factually correct, and the second statement provides the correct geomorphic explanation for the first. Verification / Alternative check: To verify, one can recall classic field examples of glacial troughs such as those in alpine regions. Photographs and diagrams show broad, flat or gently graded floors that contrast clearly with the sharp V shaped profiles left by river erosion. Geomorphology texts emphasise that this form develops because of the extensive bedrock erosion by glaciers, which tends to act across the whole valley cross section, supporting the explanation in Statement II. This agreement with the standard model of glacial erosion confirms that the given combination is correct. Why Other Options Are Wrong: Both true but Statement II not the explanation: This ignores the direct causal link between uniform glacial erosion and flat valley floors, which is central to understanding glacial trough formation. Statement I true, Statement II false: Uniform glacial erosion is not false; it is the accepted explanation for the valley floor shape. Statement I false, Statement II true: Statement I is not false, because flat floors in glacial troughs are well documented. Common Pitfalls: Some learners may confuse glacial troughs with river valleys and incorrectly expect a V shaped cross section, leading them to question Statement I. Others might think that glaciers erode only at certain points rather than relatively uniformly along the valley floor, causing doubt about Statement II. Remember that glaciers, unlike narrow rivers, can fill a valley and erode broadly, transforming the original shape into a typical U shaped trough with a comparatively flat floor. Final Answer: Both statements are individually true, and Statement II is the correct explanation of Statement I.

Question 19

Tides: Statement I says that tides are the rise and fall of sea levels caused by the combined effects of gravitational forces exerted by the Moon and the Sun and by the rotation of the Earth, and Statement II says that the Earth rotates from west to…

Accepted Answer

Introduction / Context: This question explores the causes of ocean tides and the rotation of the Earth using an assertion and reason format. The learner must decide if each statement is correct and whether the second statement logically explains the first. Tides are a fundamental part of physical geography and oceanography, while the direction of Earth rotation is a basic fact of astronomy and Earth science. Given Data / Assumptions: Statement I: Tides are the rise and fall of sea levels caused by the combined effects of gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. Statement II: The Earth rotates from west to east. We consider standard definitions of tides and accepted information about Earth rotation. Concept / Approach: Tides mainly result from the gravitational pull of the Moon and the Sun on the Earth oceans and from the centrifugal force associated with the Earth Moon system. The rotation of the Earth influences the timing and distribution of tides but is not the primary cause in the same sense as gravity. The direction of rotation, west to east, is a correct fact but does not directly explain why tides rise and fall. The approach is to separate correctness of facts from explanatory relationships. Step-by-Step Solution: Step 1: Check Statement I. Tides do arise from gravitational forces of the Moon and the Sun, and the rotating Earth influences how tidal bulges move relative to coastlines, so Statement I is substantially correct in describing the combined effects. Step 2: Check Statement II. It is a basic astronomical fact that the Earth rotates from west to east, which causes the apparent daily motion of the Sun from east to west in the sky, so Statement II is true. Step 3: Evaluate the explanatory link. While Earth rotation affects when a particular location faces a tidal bulge, the specific fact that the rotation is from west to east is not the key explanatory detail for the rise and fall of sea levels described in Statement I. Step 4: The main explanation for tides lies in gravitational attraction and the resulting tidal bulges, not in the simple statement of rotation direction. Step 5: Therefore, both statements are true, but Statement II does not serve as the correct explanation of Statement I. Verification / Alternative check: To verify, recall that tide producing forces are primarily calculated using gravitational equations involving the masses of the Earth, Moon, and Sun, and the distances between them. These calculations do not depend directly on whether the Earth rotates eastward or westward, even though rotation affects local timing of tides. If the Earth could hypothetically rotate in the opposite direction, tides would still be generated by gravity. This shows that Statement II, while true, is not the cause or explanation for the existence of tides as described in Statement I. Why Other Options Are Wrong: Both true and Statement II explains Statement I: Incorrect because the direction of rotation does not explain the fundamental origin of tides. Statement I true, Statement II false: Statement II is a well known fact, so this combination is wrong. Statement I false, Statement II true: Statement I correctly attributes tides to gravitational forces and Earth rotation, so it is not false. Common Pitfalls: Learners sometimes think that any true fact given as a second statement must automatically be the explanation of the first, which is not the case in assertion reason questions. Another common mistake is to overemphasise Earth rotation and underemphasise gravity in understanding tides. Remember that gravity from the Moon and the Sun is the primary cause of tidal bulges, while Earth rotation influences how these bulges move relative to coastlines but does not serve as the core explanatory factor being tested here. Final Answer: Both statements are individually true, but Statement II is not the correct explanation of Statement I.

Question 20

In a photographer flashgun, bright light is observed when it is fired. This intense brightness is mainly due to the presence of which noble gas in the flash tube?

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Introduction / Context: This question concerns basic applied physics and chemistry, specifically about the gases used in photographic flashguns. When a camera flash is triggered, a brief but extremely bright burst of light is produced. Many flash tubes use noble gases to generate this light by passing a high voltage through the gas. The learner needs to recall which noble gas is most commonly associated with intense, white flash light in professional and photographic equipment. Given Data / Assumptions: The device mentioned is a photographer flashgun, which uses a flash tube. The options are the noble gases argon, xenon, neon, and helium. We assume standard descriptions of gases used in photographic flash tubes as given in physics and general science references. Concept / Approach: In a flash tube, a noble gas at low pressure emits light when an electric discharge passes through it. Different gases produce different colours and intensities of light. Neon produces a reddish orange glow, argon a bluish light, and xenon produces a very bright white or bluish white light that approximates daylight. Xenon flash tubes are widely used in photography because their spectral output is suitable for colour imaging and provides a short, intense burst of light. Step-by-Step Solution: Step 1: Recall that neon is commonly used in advertising signs and gives a reddish glow, not usually used for photographic flash where a broad spectrum white light is needed. Step 2: Recognise that argon and helium can also emit light when ionised, but their spectral characteristics and brightness are not ideal for short, intense photographic flashes. Step 3: Remember that xenon flash tubes are standard in camera flashes and strobe lights because they produce an intense white flash approximating daylight conditions. Step 4: The question mentions the brightness of the photographer flashgun, which matches the known properties of xenon as used in flash tubes. Step 5: Therefore, the noble gas responsible for the bright light emission is xenon. Verification / Alternative check: A quick verification is to think about the common term xenon flash which appears in specifications for cameras, mobile phones, and studio equipment. Technical descriptions of flash units specifically refer to xenon flash tubes. In contrast, neon is rarely mentioned in relation to photography flashes. Checking this association from multiple contexts confirms that xenon is the correct answer for the gas responsible for the intense bright light in a photographer flashgun. Why Other Options Are Wrong: Argon: Although argon can be used in certain lighting applications, it is not the standard gas for photographic flash tubes. Neon: Produces a distinctive red or orange glow used in signs, not the bright white light required for flash photography. Helium: Used in some discharge lamps and scientific setups, but not the usual choice for camera flashguns. Common Pitfalls: Students may guess based on familiarity with neon signs or argon filled bulbs, leading to incorrect answers. Another pitfall is treating all noble gases as interchangeable. In reality, each noble gas has its own emission spectrum, and only xenon provides the intense, broad spectrum light that is ideal for photographic use. Remember that the specific phrase xenon flash is strongly associated with camera technology and can be used as a memory aid. Final Answer: The bright light in a photographer flashgun is primarily due to the presence of xenon gas in the flash tube.

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