Which of the following statements regarding insolation is/are correct?

Which of the following statements regarding insolation is/are correct?

  • 1. Insolation is predominantly short-wave radiation, with wavelengths in the range of 0.39 micrometre to 0.76 micrometre.
  • 2. Insolation is evenly distributed across the Earth because of the Earth’s curved surface.

Select the correct answer using the code given below.

1 only
2 only
Both 1 and 2
Neither 1 nor 2
This question was previously asked in
UPSC CDS-1 – 2024
Statement 1 is correct regarding insolation. Statement 2 is incorrect.
Insolation (incoming solar radiation) is predominantly in the form of short-wave radiation, primarily visible light. However, its distribution across the Earth’s surface is highly uneven due to factors like the Earth’s curvature, axial tilt, rotation, and atmospheric conditions.
1. Solar radiation covers a spectrum from ultraviolet to infrared. The visible light portion (approximately 0.39 to 0.76 micrometre) constitutes the peak intensity and a large proportion of the total solar energy, hence it is considered predominantly short-wave radiation.
2. The Earth’s curved surface means that the angle at which solar rays strike the surface varies with latitude. Rays hit more directly (perpendicularly) near the equator and more obliquely near the poles, spreading the energy over a larger area and thus reducing the intensity per unit area at higher latitudes. This, along with atmospheric effects and albedo differences, leads to significant variations in insolation received across the globe, making the distribution uneven.
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