What is the shape of the wavefront in each of the following cases ?
(a) light diverging from point source.
(b) light emerging out of a convex lens when a point source is placed at its focus.
( c) the portion of the wavefront of light from a distant star intercepted by earth.

Explanation

(a) The shape of the wavefront in case of a light diverging from a pointa source is spherical . The wavefront emanting from a point source is sourcce is shown in the given figure .

(b) the shape of the wavefront in case of a light emerging out ofa conex lens when a point source is placed at its forus is a parallel grid , this si shown in the given figure .

(c) the portion of the wavefront of light from a distant star intercepteed by the Earth is a plane .