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Question
How does refraction take place in the atmosphere? Why do stars twinkle but not the planets?
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Solution
There are several layers present in the atmosphere. The upper layer is optically rare, but the bottom layer is optically denser. When light passes through thicker and denser layers of the atmosphere, it bends towards the normal. As the stars are present very far away from us, the light coming from them get refracted multiple times and that results in the twinkling of the stars.
The planets are present much closer to the earth as compared to stars which make planets look like an extended source of light, not like a point-sized source of light as stars appear. This makes planets look stationary, not twinkling like stars.
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RELATED QUESTIONS
What is atmospheric refraction? Use this phenomenon to explain the following natural events:
Twinkling of stars
Draw diagrams to illustrate your answers.
The correct sequencing of angle of incidence, angle of emergence, angle of refraction and lateral displacement shown in the following diagram by digits 1, 2, 3 and 4 is:
(a) 2, 4, 1, 3
(b) 2, 1, 4, 3
(c) 1, 2, 4, 3
(d) 2, 1, 3, 4
Name two effects produced by the atmospheric refraction.
Atmospheric refraction causes advance sunrise and delayed sunset. By how much time is:
sunset delayed?
Why do stars seem higher than they actually are? Illustrate your answer with the help of a diagram.
What is atmospheric refraction?
The twinkling of stars is due to atmospheric:
(a) reflection of light
(b) dispersion of light
(c) interference of light
(d) refraction of light
The atmospheric refraction of light causes the twinkling of:
(a) planets only
(b) stars only
(c) planets and stars
(d) stars and satellites
The stars appear higher in the sky than they actually are, due to:
(a) diffraction of light
(b) scattering of light
(c) refraction of light
(d) reflection of light
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
We know that light refracts (or bends) when it goes from one medium to another. Now, the atmosphere contains only air. Then how does light get refracted on passing through only air in the atmosphere?
By how much time the day would have been shorter if the earth had no atmosphere?
A student claims that because of atmospheric refraction, the sun can be seen after it has set, and the day is, therefore, longer than if the earth had no atmosphere.
- What does the student mean by saying that the sun can be seen after it has set?
- Do you think that the students’ conclusion is correct?
Why does the sky appear blue on a clear day?
Which of the following is not caused by the atmospheric refraction of light?
(a) twinkling of stars at night
(b) sun appearing higher in the sky than it actually is
(c) sun becoming visible two minutes before actual sunrise
(d) sun appearing red at sunset
Refraction of light by the earth’s atmosphere due to variation in air density is called ____________.
Assertion: Sky appears blue in the day time.
Reason: White light is composed of seven colours.
Explain the refraction of light through a triangular glass prism using a labelled ray diagram. Hence define the angle of deviation.
