Explanation: The atmosphere is largely transparent to short wave solar radiation. The incoming solar radiation passes through the atmosphere before striking the earth’s surface.

• Within the troposphere water vapour, ozone and other gases absorb much of the near infrared radiation.
• Very small-suspended particles in the troposphere scatter visible spectrum both to the space and towards the earth surface. This process adds colour to the sky.
• The red colour of the rising and the setting sun and the blue colour of the sky are the result of scattering of light within the atmosphere.
• The insolation received at the surface varies from about 320 Watt/m2 in the tropics to about 70 Watt/m2 in the poles.
• Maximum insolation is received over the subtropical deserts, where the cloudiness is the least. Equator receives comparatively less insolation than the tropics.

Source: NCERT – Fundamental of Physical Geography