Electrostatic Potential

To solve the problem, we need to determine the shape of wavefronts for light incident on and reflected from a concave mirror, when a point source is placed at its focus.

1. Understanding Wavefronts from a Point Source:
A point source placed at the focus of a concave mirror emits spherical wavefronts. As the light rays travel toward the mirror, they are in the form of diverging spherical wavefronts.

2. Behavior at the Mirror (Reflection):
For a concave mirror, if the point source is exactly at the focus, the reflected rays become parallel to the principal axis (paraxial approximation). This results in planar (plane) wavefronts after reflection.

3. Conclusion:
- Incident wavefronts = spherical (from point source)
- Reflected wavefronts = planar (after reflection from mirror)

Final Answer:
The shapes of the wavefronts of incident and reflected lights respectively are spherical and planar.