Question

A ray of light is incident on a concave mirror. It is parallel to the principal axis and its height from principal axis is equal to the focal length of the mirror. The ratio of the distance of point B from the pole to the distance of the pole from the centre of curvature is (AB is the reflected ray)

• A. $\frac{2}{\sqrt{3}}$
• B. $\frac{\sqrt{3}}{2}$
• C. $\frac{2}{3}$
• D. $\frac{1}{2}$

Answer 1

The correct option is D $\frac{1}{2}$

Reflected ray passes through the focus. Hence, distance of B from the center of curvature is $f$ where $f$ is the focal length.

Distance of center of curvature to the pole is equal to the radius of curvature $=R=2f$

Ratio of the two distances is $\frac{1}{2}$