Question

The amount of solar radiation by the surface of the earth is called ___________.
A) Solar light
B) Heat balance
C) Terrestrial radiation
D) Insolation

Answer 1

Hint:
Almost all of the energy that the earth receives is received from the sun. In turn, it radiates the energy that it receives from the sun back to space. As a result, the earth neither gets cold nor does it warm up over a period of time. Thus, the amount of heat is not the same received by different parts of the earth.

Complete Answer:
Most of the energy that the earth’s surface receives is received in short wavelengths. The energy received by the earth is called incoming solar radiation which in short is known as insolation.
During a day, in a season, and in a year, the intensity and the amount of insolation keep varying. The variations in insolation are caused by these factors: The rotation of the earth on its axis; the angle of inclination of the sun’s rays; the length of the day; the transparency of the atmosphere; the configuration of land in terms of its aspect.
The last two, however, have less influence. The angle that the earth makes with its orbital plane around the sun i.e. $66.5^\circ $ has a greater influence on the amount of insolation received at different latitudes. The second factor depends on the latitude of a place. The lesser the angle the higher is the latitude they make with the surface of the earth resulting in slant sun rays and more absorption, scattering, and diffusion occurs when these rays are passed through a greater depth of the atmosphere. The atmosphere is mostly transparent to shortwave solar radiation. Before striking the earth’s surface the incoming solar radiation passes through the atmosphere. Within the troposphere ozone, water vapor, and other gases absorb much of the near-infrared radiation. In the troposphere, very small-suspended particles scatter visible spectrum both to the earth’s surface and towards space. This process adds color to the sky. The blue color of the sky and the red color of the rising and the setting sun are the results of the scattering of light within the atmosphere.

Thus, option (D) is correct.

Note:
The solar output received at the top of the atmosphere varies slightly in a year due to the variations in the distance between the earth and the sun.