# How can I calculate the focal point of concave mirror?

##### 1 Answer
Feb 16, 2016

$f = \frac{R}{2}$
$f = \frac{i \cdot o}{i + o}$

#### Explanation:

$\text{f:focal point}$
$\text{R:the center of curvature}$
$\text{i:distance between image and vertex(mirror's center)}$
$\text{o: distance between object and vertex}$
$f = \frac{R}{2}$
$\text{or}$
$\frac{1}{f} = \frac{1}{o} + \frac{1}{i}$
$\frac{1}{f} = \frac{i + o}{i \cdot o}$
$f = \frac{i \cdot o}{i + o}$