The setting sun often looks oval in shape because of
A. Optical illusion
B. Dispersion
C. Refraction of rays of sun passing through the atmosphere
D. None of these

Hint: We know that reflection involves a change in direction of waves when they bounce off a barrier. Refraction of waves involves a change in the direction of waves as they pass from one medium to another. Refraction, or the bending of the path of the waves, is accompanied by a change in speed and wavelength of the waves. Refraction is an effect that occurs when a light wave, incident at an angle away from the normal, passes a boundary from one medium into another in which there is a change in velocity of the light. The wavelength decreases as the light enters the medium and the light wave changes direction.

Complete step by step answer
We know that the setting sun often looks oval in shape because of refraction of rays of sun passing through the atmosphere This is due to the refraction of light coming from the sun. When light comes from the sun it generally travels from rarer medium to denser medium i.e., it travels from space to the atmosphere.
Early sunrise - It is due to that when the sun is below the horizon at that time the light from the sun enters the atmosphere from space to get refracted away from the normal line of sun and it causes early sunrise.
Delayed sunset - It is due to the reason that when the sun goes below the horizon at that time the sun light passes from space to atmosphere and it again gets refracted from the normal line of the sun and it causes the delayed sunset.
Since, refraction of rays of sun passing through the atmosphere is the reason for the oval appearance of the sun.

the correct answer is Option C.

Note: It can be concluded that for refraction to occur substances must be transparent and light ray must pass from region of one index of refraction to another i.e. both substances should have different refractive indices should and the light ray must impinge at an angle other than normal which must not be less than the critical angle. The first law of refraction states that the incident ray, refracted ray and the normal all lie in the same plane. The second law of refraction states that the ratio of sine of angle of incidence to the sign of angle of refraction is constant to the interface of any two-given medium.