Question

The radius of curvature of a spherical mirror is 20cm. what is its focal length?

Answer 1

HEY MATE....
HERE'S THE ANSWER
f=R/2
f=20/2= 10 cm....ans

hope it will help you

Answer 2

$\Large\sf\red{Question:}$

The radius of curvature of a spherical mirror is 20cm. What is its focal length?

$\Large\sf\red{Solution:}$

☞Given:

Radius of curvature = 20cm

☞To find:

Focal length = ?

☞Formula used:

f = $\sf\dfrac{R}{2}$

where, f = focal length , R = radius of curvature.

Spherical mirror may be either convex mirror or concave mirror.

$\tt\orange{For\:Convex\:Mirror:}$

Radius of curvature (R) = + 20cm

Focal length (f) = ?

We know ,

f = $\sf\dfrac{R}{2}$

f = $\sf\dfrac{20}{2}$

f = $\cancel\dfrac{20}{2}$

✒f = 10cm.

$\tt\orange{For\:Concave\:Mirror:}$

Radius of curvature (R) = - 20cm

Focal length (f) = ?

We know that ,

f = $\sf\dfrac{R}{2}$

f = $\sf\dfrac{-20}{2}$

f = $\cancel\dfrac{-20}{2}$

✒f = -10cm.

Therefore,

✒Focal length of a covex mirror is 10cm

✒Focal length of a concave mirror is -10cm.