Atmospheric pressure exerted on the Earth's surface is mainly due to which of the following?

Introduction / Context:
Atmospheric pressure is the force per unit area exerted on the Earth's surface by the weight of the air above it. This question asks you to identify the main cause of this pressure. Understanding this concept helps explain weather patterns, barometer readings and why pressure decreases with altitude.

Given Data / Assumptions:

• The Earth is surrounded by an atmosphere composed of gases such as nitrogen and oxygen.
• The atmosphere has mass and is influenced by physical forces.
• We are concerned with the overall force that produces the measurable air pressure at the surface.
• Effects such as rotation and heating may influence distribution but not the basic existence of pressure.

Concept / Approach:
Atmospheric pressure exists because air has weight. Air molecules are pulled toward the Earth by gravity, just as any object with mass is attracted. This gravitational attraction compresses the air near the surface, making it denser and causing it to exert a force on everything below. Rotation, revolution and uneven heating affect wind patterns, circulation and local pressure variations, but they do not create the basic vertical weight of the air. The fundamental source of atmospheric pressure is the gravitational pull of the Earth on the air column above each area.

Step-by-Step Solution:
Step 1: Recognise that atmospheric pressure is defined as the weight of the air per unit area. Step 2: Weight is the result of gravitational force acting on mass, here the mass of the air molecules. Step 3: The Earth's gravity pulls air downward, compressing it more strongly near the surface. Step 4: This compressed air exerts a force on surfaces in contact with it, which we measure as atmospheric pressure. Step 5: Therefore, the direct cause of atmospheric pressure is the gravitational pull of the Earth on the atmosphere.

Verification / Alternative check:
If the Earth had no gravity, air molecules would not be held near the surface; they would disperse into space and no significant atmospheric pressure would exist at ground level. Barometric pressure decreases with altitude because there is less air above and therefore less weight pressing down, again showing the role of gravity. Rotation and uneven heating do change the distribution of pressure horizontally (creating high and low pressure areas), but they do not create the fundamental downward force itself.

Why Other Options Are Wrong:
Rotation of the Earth on its axis: This contributes to phenomena like the Coriolis effect and wind patterns but is not the basic cause of atmospheric pressure.

Revolution of the Earth around the Sun: This affects seasons and climate but does not directly produce the weight of the atmosphere.
Uneven heating of the Earth's surface: This creates local pressure differences and winds, but the existence of pressure itself depends on gravity acting on the air mass.

Common Pitfalls:
Students sometimes attribute all atmospheric effects to rotation or heating because they learn about these processes in weather units. However, the key idea is that without gravity, there would be no significant atmosphere and no pressure to measure. Always separate the cause of pressure (gravity acting on mass) from the factors that redistribute pressure (heating, rotation and topography).

Final Answer:
Atmospheric pressure on Earth is mainly due to the Gravitational pull of the Earth on air.