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What is meant by atmospheric refraction of light ? Explain the following natural phenomenon by using the concept of atmospheric refraction :
(a) Twinkling of stars
(b) Flickering of objects seen through a turbulent stream of hot air
(a) Twinkling of stars
(b) Flickering of objects seen through a turbulent stream of hot air
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$\bullet$ Refraction of light by the earth's atmosphere due to variation in
optical density of different layers of air is called as atmospheric
refraction. (1)
(a) The starlight, on entering the earth's atmosphere undergoes
refraction continuously in a medium of gradually increasing
refractive index and we see the apparent position of the star. Since
the physical conditions of atmosphere are not stationary, the
apparent position of the star fluctuates and gives twinkling effect. (1)
(b) The air just above the fire becomes hotter than the air further up.
The hotter air is lighter (less dens) than cooler air above it and has a
refractive index slightly less than that of cooler air. Since the
physical conditions of refracting medium are not stationary, the
apparent position of objects, as seen through hot air fluctuates. And
we see flickering objects. (1)
optical density of different layers of air is called as atmospheric
refraction. (1)
(a) The starlight, on entering the earth's atmosphere undergoes
refraction continuously in a medium of gradually increasing
refractive index and we see the apparent position of the star. Since
the physical conditions of atmosphere are not stationary, the
apparent position of the star fluctuates and gives twinkling effect. (1)
(b) The air just above the fire becomes hotter than the air further up.
The hotter air is lighter (less dens) than cooler air above it and has a
refractive index slightly less than that of cooler air. Since the
physical conditions of refracting medium are not stationary, the
apparent position of objects, as seen through hot air fluctuates. And
we see flickering objects. (1)