Explain with a suitable diagram, how a concave mirror converges a parallel beam of light rays. Mark clearly the pole, focus and centre of curvature of concave mirror in this diagram.

When a parallel beam of light rays, which are also parallel to the principal axis of a concave mirror, converge at the principal focus $(F)$ after getting reflected from the mirror.  Since a concave mirror converges a parallel beam of light rays, it is also known as a converging mirror.

Ray diagram- A concave mirror converges a parallel beam of light rays.