Question

what is atmospheric refeaction?use this example explain twinkling of stars.

Answer 1

It's cause by optical illusion

Answer 2

Refraction caused by the atmosphere due to the varying optical densities in the different air layers is called atmospheric refraction.
Twinkling of stars is due to atmospheric refraction. The light from the stars on entring earths atmosphere undergoes refraction. This because of the different optical densities of the layers of atmosphere. The atmosphere is continuously changing. The changing atmosphere refracts the light by different measures form one moment to the other. When the atmosphere refracts more star light stars appear bright and when atmosphere refracts less light then stars appear dim.
The light entering our eyes increases and decrease continuously which causes the twinkling effect.