Question

Twinkling of stars is due to
(a). Refraction of light
(b). Refraction of light
(c). Diffraction
(d). All

Answer 1

Hint: Stars appear as brighter as well as fainter when we look at them. This is known as the twinkling of stars. Earth is consisting of various layers of atmosphere with different physical conditions. These conditions will change the direction of light rays coming from the stars. This leads to the twinkling of stars.

Complete step-by-step solution -

Most of the people believe that stars are twinkling. Even our poems are also teaching that. But it is entirely wrong. It appears as twinkling since we are looking at the stars from our earth. If we are looking at them from space, then it will look like a permanently glowing object.
This twinkling of stars is because of the refraction of light rays. When the light ray travels from one medium to another medium, the light ray bends towards or away from the normal according to the density of the two media. Actually because of the refraction the speed of the light changes according to the medium.
Our earth atmosphere consists of several layers of various components. These layers have different physical conditions like temperature, pressure, density etc. So, when the light coming from a star undergoes multiple times of refraction at various levels. Because each layer around the earth is not similar and not uniformly distributed. Each layer has its own specific refractive index. So, it will look like a turbulent flow of water. Since the distance from the star is very large, it will take more time to reach the light in the earth. So, the movement of the star and the time taken for the light to reach the earth will fluctuate in brightness to our eyes. These multiple refractions and the movement of stars makes a twinkling effect to our eyes.

Hence the correct option is A, refraction of light.

Note: If the earth doesn’t have an atmosphere, then the light from the star will travel through a straight line instead of taking a zig-zag path. The density, temperature and components of layers of atmosphere can make an impact on the refractive indices of each layer. Thus, it can be the reason for the twinkling of stars. Diffraction of the light is the reason for the sun appearing red during sunset.