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Which of the following causes the colour of the clear sky to appear blue at noon?
AReflection from oceans
BAtmospheric dust in the standard view
CAbsorption of red by air
DSelective scattering of shorter wavelengths
Answer & Solution
Correct answer: D. Selective scattering of shorter wavelengths
1. Sunlight contains all visible colours.
2. Air molecules scatter shorter wavelengths much more than longer ones.
3. Blue light, being short, is scattered in all directions across the sky.
4. Observers receive this scattered blue light from every direction overhead.
5. The sky therefore looks blue.
6. So selective scattering of short wavelengths is the cause.
_Source: NCERT Class 10 Science Ch 11 'Human Eye and the Colourful World'_
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