Question

The radius of curvature of a concave mirror is 30cm. What is the focal length of this mirror?¿

Answer 1

Given:-

The radius of curvature of a concave mirror is 30cm.

• R= 30cm

To Find:-

• focal length of this mirror.

Solution:-

Focal length:-The distance from the lens to the focal point is called the focal length.

For converging lenses, the focal length is always positive, while diverging lenses always have negative focal lengths.

Formula of Focal length:

$\mathcal{\underbrace{\overbrace{\mid{\blue{\sf R=2F }}\mid}}}$

i.e, Radius = twice of it's focal length

So,

$=>R= 2 \times F$

$= > F = \frac{R}{2}$

$= > F = \frac{30cm}{2}$

$= > F = 15cm$

∴ the focal length of this mirror is 15cm.