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Question
Why does the sky appear blue on a clear day?
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Solution
The sky appears blue on a clear day because of the scattering of blue light by the air molecules in the earth's atmosphere. The air molecules are much smaller compared with the wavelength of visible light. Therefore, they scatter light of shorter wavelengths more easily and effectively than light of longer wavelengths. Hence, blue light gets scattered very easily because of its shorter wavelength compared with other colours, such as red, orange and yellow.
RELATED QUESTIONS
Explain why the planets do not twinkle.
Name the phenomenon which causes the twinkling of stars.
Name two effects produced by the atmospheric refraction.
Atmospheric refraction causes advance sunrise and delayed sunset. By how much time is:
sunset delayed?
Fill in the following blank with suitable word:
We can see the sun about ................ minutes before the actual sunrise and about ................ minutes after the actual sunset because of atmospheric ................
Why do stars seem higher than they actually are? Illustrate your answer with the help of a diagram.
The twinkling of stars is due to atmospheric:
(a) reflection of light
(b) dispersion of light
(c) interference of light
(d) refraction of light
As light from a far off star comes down towards the earth:
(a) it bends away from the normal
(b) it bends towards the normal
(c) it does not bend at all
(d) it is reflected back
Due to atmospheric refraction of sunlight, the time from sunrise to sunset is lengthened by about:
(a) 6 minutes
(b) 2 minutes
(c) 4 minutes
(d) 5 minutes
The day is longer on the earth by about 4 minutes because:
(a) the earth is round in shape
(b) the earth rotates on its axis
(c) the earth revolves around the sun
(d) the earth has atmosphere
State one effect produced by the scattering of light by the atmosphere.
A star sometimes appears brighter and some other times fainter. What is this effect called? State the reason for this effect.
The stars appear higher from horizon than they actually are. Explain why it is so.
Explain why the planets do not twinkle but the stars twinkle.
Assertion: Sky appears blue in the day time.
Reason: White light is composed of seven colours.
How does refraction take place in the atmosphere? Why do stars twinkle but not the planets?
