Question

A concave mirror has been used to focus the incident beam of paraxial rays at a point. To achieve the highest accuracy while converging the beam to a point, the mirror used should have:

• A. aperture comparable to its radius of curvature
• B. very small aperture compared to its radius of curvature
• C. very large aperture compared to its radius of curvature
• D. aperture of mirror doesn't have significant role

Answer 1

The correct option is B very small aperture compared to its radius of curvature


In order to focus the incident beam concisely to a single point, the region of the incoming incident beam needs to be restricted. This can be achieved by using a concave mirror with very small aperture$\left(AB\right)$ compared to its radius of curvature.