Question 1

Atmospheric optics vocabulary: Which natural phenomenon is called 'deer's thirst' (Mṛga–tṛiṣṇā) in Sanskrit?  The classical Sanskrit term refers to an optical illusion seen over hot surfaces in deserts or roads. Choose the correct option.

Accepted Answer

ConceptMṛga–tṛiṣṇā literally “deer’s thirst” denotes a mirage, an illusion of water due to refraction in heated air layers.Final AnswerMirage

Question 2

Vehicle dynamics on a circular track: Maximum speed before overturn (data incomplete).  A car moves on a level circular track of radius 100 m; the coefficient of friction between tyre and road is 0.2. Choose the correct option.

Accepted Answer

≈ 50.4 km/h

Question 3

Metric prefixes: Convert nanometre to metre.  One nanometre (nm) equals what fraction of a metre (m)? Choose the correct option.

Accepted Answer

ConceptSI prefix nano = 10−9.Final Answer10−9 metre

Question 4

Astronomy instrumentation: Why radio telescopes can outperform optical ones in some situations.  Consider operating conditions and the ability to observe through clouds and interstellar dust. Choose the correct option.

Accepted Answer

ConceptRadio wavelengths are weakly affected by clouds and can penetrate interstellar dust better than optical light.Thus, radio telescopes can observe day/night and in suboptimal weather; with interferometry they also achieve high angular resolution.Final AnswerThey can operate day and night and through clouds/dust with minimal attenuation

Question 5

Stellar distances and light travel time: Alpha Centauri to Earth.  Alpha Centauri is the nearest star system after the Sun; estimate the time its light takes to reach Earth. Choose the correct option.

Accepted Answer

ReasoningAlpha Centauri is ~4.3 light-years away; 1 light-year is the distance light travels in one year.Final AnswerAbout 4.3 years

Question 6

Formation of a rainbow: Which phenomena are essential?  Sunlight falls on raindrops; identify the correct combination from the listed phenomena. Choose the correct option.

Accepted Answer

ConceptA primary rainbow forms due to refraction at entry, internal reflection inside the drop, and dispersion (wavelength-dependent refraction).NoteThe list uses “diffusion”; the physically relevant term is dispersion. Among the listed choices, the best correct pair is refraction + internal reflection.Final AnswerRefraction and internal reflection

Question 7

Acoustics: Name for sound below the human hearing threshold.  Sounds with frequency lower than 20 Hz are termed as what? Choose the correct option.

Accepted Answer

ConceptHuman hearing ≈ 20 Hz to 20 kHz. 20 kHz: ultrasound.Final AnswerInfrasonic (infrasound)

Question 8

Why do large transformers heat up? Identify the dominant causes.  Large power transformers heat and are oil-cooled; select the main physical loss mechanisms causing the heating. Choose the correct option.

Accepted Answer

ConceptCore (iron) losses: hysteresis + eddy currents in the magnetic core.Copper losses: I²R heating in primary and secondary windings.Final AnswerCore losses (hysteresis and eddy currents) and copper losses (I²R in windings)

Question 9

Apparent motion of stars: East-to-west drift explained.  Why do stars seem to move from east to west across the sky to an observer on Earth? Choose the correct option.

Accepted Answer

ConceptEarth's rotation is west → east; this makes the celestial sphere appear to move east → west.Final AnswerBecause Earth rotates from west to east

Question 10

Projectile from a plane: Horizontal range of a dropped bomb.  A plane flies horizontally at 600 km/h at a height of 1,960 m. When vertically above point A, a bomb is released and strikes at point B. Find distance AB. Choose the correct option.

Accepted Answer

Given dataHeight, h = 1960 mHorizontal speed, v = 600 km/h = 600 × (1000/3600) = 166.67 m/sAcceleration due to gravity, g = 9.8 m/s² (downward)Step 1: Time of fallh = (1/2) g t² ⇒ t = √(2h/g) = √(2 × 1960 / 9.8) = √400 = 20 sStep 2: Horizontal distanceRange R = v × t = 166.67 × 20 = 3333.4 m ≈ 3.33 kmVerificationUnits consistent; height chosen to make t an integer (20 s), confirming the arithmetic.Final Answer3.33 km (approximately)

Question 11

Origin of atmospheric radiocarbon (C-14): Formation mechanism.  Identify how radiocarbon is generated naturally in Earth’s atmosphere. Choose the correct option.

Accepted Answer

ConceptPrimary mechanism: cosmic rays produce fast neutrons which convert atmospheric ¹⁴N to ¹⁴C.Final AnswerCosmic ray neutrons interacting with nitrogen-14 (n + ¹⁴N → ¹⁴C + p)

Question 12

Applications of RADAR: Core functionality.  What is RADAR primarily used for in practical systems (aviation, maritime, meteorology)? Choose the correct option.

Accepted Answer

ConceptRADAR = RAdio Detection And Ranging.Locates objects and measures range, bearing, and via Doppler, speed.Final AnswerDetecting and determining range/direction (and often speed) of objects

Question 13

Fluid dynamics & flight: Use of Mach number.  Mach number relates an object’s speed to the local speed of sound in the medium. Choose the correct option.

Accepted Answer

ConceptMach number = object speed / speed of sound (subsonic, transonic, supersonic, hypersonic regimes).Final AnswerAircraft and high-speed gas flows (speed relative to sound)

Question 14

Speed of sound travel-time puzzle: Two listeners hear the same sound at 5 s and 6 s.  Speed of sound = 300 m/s. Find the maximum and minimum possible distances between the two persons. Choose the correct option.

Accepted Answer

GivenSpeed of sound, v = 300 m/sArrival times: 5 s and 6 sStep 1: Convert times to distances from sourced1 = v × 5 = 300 × 5 = 1500 md2 = v × 6 = 300 × 6 = 1800 mStep 2: Use triangle inequality for possible placementsMaximum separation when persons are on opposite sides of the source: dmax = d1 + d2 = 1500 + 1800 = 3300 m.Minimum separation when they are colinear on the same side: dmin = |d2 − d1| = 1800 − 1500 = 300 m.Final AnswerMaximum 3300 m; Minimum 300 m

Question 15

Brilliant colours in thin oil films on water: Identify the cause.  Small oil films on water on a rainy day show vivid colours due to a wave-optics effect. Choose the correct option.

Accepted Answer

ConceptVarying film thickness causes path difference between rays reflected from the top and bottom interfaces.Constructive/destructive interference at different wavelengths produces colours.Final AnswerInterference of light in thin films (with reflection)

Question 16

Basic astronomy facts: What are planets?  Choose the most accurate description of planets in a solar system. Choose the correct option.

Accepted Answer

Non-luminous bodies that reflect sunlight and revolve around a star

Question 17

Acoustics and inverse-square law: How does sound intensity vary with distance from a point source?  Assume an ideal point source radiating uniformly in all directions in free space; neglect absorption and reflections.  Choose the correct proportiona…

Accepted Answer

Concept/ApproachFor a point source emitting acoustic power P uniformly, the power spreads over the surface of a sphere 4πr2. Intensity I = P / (4πr2), hence I ∝ 1/r2.Step-by-stepI(r) = P / (4πr2)⇒ doubling r reduces I by a factor of 4.Common pitfallsConfusing amplitude (∝ 1/r) with intensity (∝ amplitude² ⇒ 1/r²).Final AnswerInversely proportional to r² (square of the distance)

Question 18

Solid-state physics: Why are metals good conductors of electricity?  Select the primary microscopic reason for high electrical conductivity in metals at ordinary temperatures.  Choose the correct option.

Accepted Answer

ConceptIn metals, valence and conduction bands overlap or the conduction band is partially filled. Electrons are delocalized ('free'), allowing drift under an electric field ⇒ high conductivity.ContrastInsulators have large band gaps; semiconductors have fewer carriers at room temperature unless doped.Final AnswerDue to the presence of many free (delocalized) electrons in a conduction band

Question 19

Electronics basics: What conversion do rectifiers perform in electric circuits?  Identify the input–output conversion done by a diode-based rectifier in power supplies.  Choose the correct option.

Accepted Answer

ConceptA rectifier (half-wave, full-wave, or bridge) uses diodes to pass current preferentially in one direction, converting alternating current to pulsating direct current, then smoothed by filters.Final AnswerAC to DC

Question 20

Celestial alignments: Under what condition does a solar eclipse occur?  Describe the relative positions of the Sun, Moon, and Earth responsible for a solar eclipse.  Choose the correct option.

Accepted Answer

ConceptA solar eclipse happens at or near new Moon when the Moon's shadow falls on Earth due to Sun–Moon–Earth alignment.Final AnswerWhen the Moon comes between the Sun and Earth (new Moon alignment)

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