What is atmospheric refraction? Use this phenomenon to explain the following natural events:
(a) Twinkling of stars
(b) Advanced sunrise and delayed sunset
Draw diagrams to illustrate your answer.
Answers
The atmospheric refraction is defined as the phenomenon of refraction of light due to change in the refractive index at different level in atmosphere. Light gets refracted at different layers of atmosphere. The air just above the radiator becomes hotter than the air farther up. Since the hotter air is less denser than the cooler air above it and has less refractive index than cooler air. The physical conditions of the atmosphere are not same, the apparent position of the object through hot air fluctuates. This is known as atmospheric refraction.
(a) Twinkling of stars:
Twinkling of stars is due to atmospheric refraction of star light. The star light after entering the earth's atmosphere undergoes refraction in a continuous manner before it reaches the Earth. The atmospheric refraction is due to change in the refractive index at different level in atmosphere. The star light bends towards the normal, the apparent position is different from the actual position of star. Since atmosphere is not stationary and keeps changing. As path of rays of light coming from star varies slightly then the apparent position of star also varies slightly and the amount of light entering the eye flickers. Sometimes, it is brighter and sometimes the star seems fainter. In this way, stars twinkle.
(b) The advance sunrise and sunset occurs due to phenomenon of atmospheric refraction. The Sun is visible to us before 2 minutes in sunrise and 2 minutes after the sunset. The actual sunrise mean the time when the sun crosses the horizon. This occurs due to refraction of light which passes through various layers of atmosphere.
Atmospheric refraction is the refraction of light in the atmosphere due to optical density the light bends according to there wave length