The shape of reflected wavefronts in case of reflection of plane wave front from concave mirror is

Options

A. Spherical
B. Plane
C. Cylindrical
D. Both (2) & (3)

Answer

To determine the shape of the reflected wavefronts when a plane wavefront reflects off a concave mirror, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Plane Wavefronts**:
A plane wavefront consists of parallel rays of light that are equidistant from each other. These rays are typically considered to be coming from a distant source.

2. **Setup of the Concave Mirror**:
We have a concave mirror with a principal axis. The center of curvature (C) and the focus (F) are important points on this mirror. The focus is located at a distance equal to half the radius of curvature (R).

3. **Incident Rays**:
When parallel rays (representing the plane wavefront) strike the concave mirror, they are incident at an angle perpendicular to the principal axis.

4. **Reflection of Rays**:
According to the laws of reflection, each ray will reflect off the mirror and converge towards the focus (F). This means that all the parallel rays that hit the mirror will reflect and meet at the focus.

5. **Shape of the Reflected Wavefront**:
Since the reflected rays converge at a single point (the focus), the shape of the reflected wavefront will be spherical. This is because, after reflection, the wavefront can be considered as originating from the focus, creating a spherical wavefront expanding outward.

6. **Conclusion**:
Therefore, the shape of the reflected wavefronts in the case of reflection of a plane wavefront from a concave mirror is spherical.

### Final Answer:
The shape of the reflected wavefronts in case of reflection of plane wavefront from a concave mirror is **spherical**.