When a plane wave front is incident on a concave mirror as shown in the figure,what is the shape of the reflected wave front?

Explain how to obtain a new wavefront at time $\tau$ using Huygens' principle for a plane wavefront.

What is the shape of the wavefront in each of the following cases:
$(a)$ Light diverging from a 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 the Earth.

The wave theory of light was given by

The speed of light in water is less than the speed of light in air,confirms the assumption of which theory of light?

What is the shape of the wavefront of light diverging from a point source?