Question

If the radius of curvature of a concave mirror is 1 m, what is its focal length?

Answer 1

1. Radius of curvature: The radius of the hollow sphere of which the spherical mirror is a part is called the radius of curvature of the spherical mirror. In other words, the distance between the pole and centre of curvature of the spherical mirror is called its radius of curvature It is denoted by R.
2. Focal length: The distance between the pole (P) and focus (F) is called the focal length (f). It is denoted by f. If f is the focal length and R is the radius of curvature, then the relation between focal length and radius of curvature is given by,

$R=2f$

or,

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

3.The value of the radius of curvature is, R = 1 m

$f=\frac{1}{2}$

$f=0.5m$

Hence focal length is .