Question

Shape of wavefront coming out of the convex lens when plane wave is incident on it

Answer 1

The shape of a wavefront in the case of light emerging out of a convex lens when a point source is placed at its focus is a parallel grid.

The illustration of this is shown in a wave grid.

Find the illustration in the image below for better understanding.

In the diagram the light source and wavefront are clearly indicated and labeled.

Answer 2

The answer is spherical.

The shape of the wavefront coming out of the convex lens when a plane wave is incident on it is spherical. This is because of the shape of the convex lens. A convex lens is thin at both the ends and comparatively thicker at the sides.