Find the focal length of a concave mirror whose radius of curvature is 32 cm.

Given:

Radius of curvature = $r$ = 32 cm = $-32$ $\left[negative\ sign\ is\ applied\ because\ the\ mirror\ is\ concave\right]$

To find: = $f$ = Focal length

Solution:

We know that the focal length of a spherical mirror is half of its radius of curvature.

Mathematically it is given as-

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

Now, putting the given value we get-

$f=\frac{1}{2}\times (-32)$ 

$f=-16cm$

Hence, the focal length of a concave mirror will be -16cm.