With reference to the Earth's atmosphere, which one of the following statements is correct?

Question

Accepted Answer

The earth’s surface receives most of its energy in short wavelengths. The energy received by the earth is known as incoming solar radiation which in short is termed as insolation. The insolation received at the surface varies from about 320 Watt/m2 in the tropics to about 70 Watt/m2 in the poles. Therefore, the total amount of insolation received at the equator is roughly about 5 times of that received at the poles. Hence option (a) is not correct.Insolation is frequently referred to as shortwave radiation; it falls primarily within the ultraviolet and visible portions of the electromagnetic spectrum and consists predominantly of wavelengths of 0.39 to 0.76 micrometres. Radiation emitted from Earth is called long-wave radiation; it falls within the infrared portion of the spectrum and has typical wavelengths of 4 to 30 micrometres. Hence option (b) is not correct.The atmosphere is largely transparent to shortwave solar radiation. The incoming solar radiation passes through the atmosphere before striking the earth’s surface. Within the troposphere, water vapor, ozone and other gases absorb much of the near infrared radiation. Water vapor is the most abundant greenhouse gas in the Earth's atmosphere, and it has strong absorption properties in the infrared portion of the electromagnetic spectrum. As infrared radiation passes through the atmosphere, water vapor molecules can absorb and re-emit a significant portion of the longwave radiation. Hence option (c) is the correct answer.Infrared waves are not part of the visible spectrum of electromagnetic waves in solar radiation. The visible spectrum refers to the range of electromagnetic waves that are visible to the human eye, which includes wavelengths between approximately 400 to 700 nanometers. Infrared waves have wavelengths longer than approximately 700 nanometers. Most of the radiation emitted by a moderately heated surface is infrared. Hence option (d) is not correct.Source Citation: NCERT: Class XI Fundamentals of Physical Geography, Chapter 9