Question

What is the distance $PA$ called?

• A. Equivalent distance
• B. Equivalent radius
• C. Radius of curvature
• D. Center of curvature

Answer 1

Answer: (C)

Radius of curvature

When the image forms on the object in a concave mirror, then the object as well as the image is situated at the center of the curvature of the concave mirror. Hence, the distance $PA$ is called as Radius of Curvature of the concave mirror.

Relation between radius of curveture(R) and focal length(f)-

$f=\frac{R}{2}$

$PB=\frac{PA}{2}$