Light from a point source in air falls on a spherical glass surface (n = 1.5 and radius of curvature = 20 cm). The distance of the light source from the glass surface is 100 cm. At what position the image is formed ?

Explanation

It is given that `u=-100 cm, R = +20 cm, n_(1) =1` (for air) and `n_(2)=1.5` (for glass)
We know that for refraction through a spherical surface `n_(1)/v - n_(1)/u = (n_(2)-n_(1))/R`
`therefore (1.5-1)/20` or `1.5/v - 1/100 = 1.5/100 rArr v= 100 cm`
Thus, the image is formed at a distance of 100 cm from the pole of spherical svirface in the direction of the incident light.