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Questions
What is atmospheric refraction? Use this phenomenon to explain the following natural events:
Twinkling of stars
Draw diagrams to illustrate your answers.
Explain with the help of a labelled diagram, the cause of twinkling of stars.
Why do stars twinkle?
Why do stars twinkle ? Explain.
Solution 1
Stars emit light on their own; when this light travels through the Earth's atmosphere which has variable optical density, the continuously changing atmosphere refracts the light from the stars in different amounts from one moment to the next. The light seems to be bright and dim as it keeps changing because of continuous refraction through the different layers of the atmosphere of the Earth. Hence, we say light twinkles at night.
Solution 2
Stars are considered to be point sources of light as they are far away from the Earth. The light coming from stars, on entering the atmosphere, gets bent because of refraction. Since the atmospheric physical conditions are continually changing, the apparent position of the star also keeps fluctuating. The amount of light entering the eye also varies because different amount of light bends at every instant. This is what gives the stars a twinkling appearance
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RELATED QUESTIONS
Atmospheric refraction causes advance sunrise and delayed sunset. By how much time is:
sunrise advanced?
State whether the following statement is true or false:
The planets twinkle at night due to atmospheric refraction of light.
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
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
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?
State two effects produced by the scattering of light by the atmosphere.
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
A star sometimes appears brighter and some other times fainter. What is this effect called? State the reason for this effect.
Explain the refraction of light through a triangular glass prism using a labelled ray diagram. Hence define the angle of deviation.
How does refraction take place in the atmosphere? Why do stars twinkle but not the planets?
