The earth atmosphere is mainly heated bywhich one of the following ?Select the correct answer from the code given below:

1. A

   Long wave terrestrial radiation

   Option (a) claims that the earth atmosphere is mainly heated by long wave terrestrial radiation. This is the correct mechanism because solar radiation passes through the atmosphere almost unheated, and the earth surface absorbs short waves and reradiates heat as long waves which warm the lower atmosphere.

2. B

   Scattered solar radiation

   Option (b) claims that scattered solar radiation is the primary heating source. While scattering diffuses light, it is not the main driver of atmospheric thermal energy compared to terrestrial reradiation.

3. C

   Reflected solar radiation

   Option (c) claims that reflected solar radiation, or albedo, heats the atmosphere. Although some solar energy is reflected back, this component contributes minimally to the overall heating of the lower air layers.

4. D

   Short wave solar radiation

   Option (d) claims that short wave solar radiation heats the atmosphere directly. Incoming solar radiation is of short wave type, but the atmosphere is relatively transparent to it, meaning it heats the earth surface rather than the air directly.

Summary. Official key is (a) because the earth atmosphere is primarily heated by long wave terrestrial radiation rather than direct incoming solar rays. Incoming solar radiation enters as short waves and passes through the atmosphere without significantly heating it. Once absorbed by the surface, this energy is transformed and radiated outward as terrestrial long waves. These long waves are effectively absorbed by greenhouse gases and water vapor in the lower atmosphere. Thus, option (a) correctly identifies the primary source of lower atmospheric heating.