Question

An object is placed to the left of a convex mirror, such that the object-to-image distance is 140 cm.

Find the focal length of the mirror, if the image is 35 cm from the mirror.

Please explain step by step as I do not know how to do this properly. Thank you!

Answer 1

The focal length of the mirror is 52.5 cm.

Step-by-step explanation:

Given that,

Object to Image distance d = 140 cm

Image distance v= 35 cm

We need to calculate the object distance

`u = d-v`

`u = 140-35=105\ cm`

We need to calculate the focal length

Using formula of mirror

`(1)/(f)=(1)/(u)+(1)/(v)`

Put the value into the formula

`(1)/(f)=(1)/(-105)+(1)/(35)`

`(1)/(f)=(2)/(105)`

`f=52.5\ cm`

Hence, The focal length of the mirror is 52.5 cm.