UPSC Prelims 2003 · General Studies
Question 31: Science and Technology
Diffusion of light in the atmosphere takes place due to
AnswerThe answer is (b).
Diffusion (scattering) of sunlight in the atmosphere is caused by the particles in it, and the key picks dust particles, which scatter light in all directions. Very fine particles and air molecules scatter short wavelengths more, which gives the blue sky, while larger dust and water droplets scatter all colours alike, which makes haze and whitish skies. Carbon dioxide and helium play almost no part in scattering visible light.
Why each option is right or wrong
- (a) Carbon dioxide is a small part of air and contributes little to scattering.
- (b) Correct: dust particles scatter light in the atmosphere.
- (c) Helium is present only in traces and plays no real part.
- (d) Water droplets can scatter light, but the key goes with dust particles.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2003, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.