By Huygen's wave theory of light,we cannot explain the phenomenon of

The wave front is a surface in which

For light diverging from a point source,

Assertion $A$: For light diverging from a point source,the intensity at the wavefront does not depend on the distance.
Reason $R$: In a diverging beam of light from a point source,a spherical wavefront is observed.

Explain the refraction of a plane wave by a thin prism.

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