Explain briefly what causes the twinkling of stars at night.
Solution :
The light from stars suffers a series of refraction due to atmospheric layers of different densities and the different refractive indices. Due to this reason, a ray of light starting from a star bends more and more towards the normal before reaching the observer on the earth. But the observer sees the star in the direction of the ray reaching finally in the eye, so star appears to him at straight path instead of curve path. On account of changes in temperature and density the apparent position of the star continually changes which gives the twinkling effect of the star.
