Question

Which of the following are examples of atmospheric refraction?
(A) Twinkling effect of stars
(B) Flattening of Sun's disc
(C) Wavering of objects in hot air
(D) All of these

Answer 1

The phenomena of bending of light rays due to change in the refractive index of the medium through which the light is travelling is named as refraction. In our atmosphere as we go up from the earth’s surface refractive index of the atmosphere changes.

Complete step by step solution:
Hot air is lighter than cool air and hence is less dense hence it’s refractive index slightly less than that of cool air. In our atmosphere, as we go up from the earth’s surface temperature of air decreases, and thus the refractive index of the atmosphere increases.
Since the particles in the refracting medium (air) don’t seem to be stationary, the position of the source of light appears to fluctuate when seen through the air.
The twinkling of a star is due to atmospheric refraction of starlight because the starlight undergoes continuous refraction before it reaches our planet. Because the path of the rays of light coming from the star goes on changing slightly, the position of the star changes continuously and also the amount of light entering the eye flickers i.e. the star sometimes appears brighter, and at another time, fainter, which produces the twinkling effect.
The flattening of the Sun's disc at sunrise and sunset is also due to the same phenomenon.
Wavering of objects in the hot air is also due to the above-mentioned phenomena but in the above case, the distance through which light passes is very-very large compared to the wavering of objects in the hot air but in the wavering of objects in the hot air is governed largely due to its closeness to the earth’s
the surface where the change in refractive index is larger with the change in height from the earth’s surface.

Hence, the correct answer is option (D) All of these.

Note:
Mirage is also formed due to a similar reason that is the change in the refractive index of air with the increase in height from the earth’s surface this is more commonly seen in deserts as there temperature is higher than other places due to which change in the refractive index also increases with the change in height from the ground.