Question

A concave mirror forms a real image of an object placed in front of it at a distance 30 cm,of size three times the size of object . Find the focal length of mirror and position of image

Answer 1

I hope it helps mate

Answer 2

The focal length of mirror and position of image is -22.5 cm and -90 cm respectively.

Explanation:

Given that,

Object distance from a concave mirror, u = -30 cm

Magnification, m = -3 (real image)

To find,

Focal length of mirror and position of image

Solution,

The magnification of the mirror is given by the ratio of image distance to the  object distance. It is given by :

$m=\dfrac{-v}{u}$

$-3=\dfrac{-v}{-30}$

v = -90 cm

Image is location at a distance of 90 cm form the mirror. Using mirror's formula to find the focal length of the mirror as :

$\dfrac{1}{f}=\dfrac{1}{v}+\dfrac{1}{u}$

$\dfrac{1}{f}=\dfrac{1}{(-90)}+\dfrac{1}{(-30)}$

f = -22.5 cm

So, the focal length of the mirror is ( -22.5 cm). Hence, this is the required solution.

Learn more,

Mirror's formula

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