Question

An object is placed infront of a convex mirror at a distance of 20cm,and its image is formed behind the mirror at a distance of 10cm,find focal length of the mirror​

Answer 1

Answer:

Hope it will help you....

Answer 2

Given :

In convex mirror,

Object distance : 20 cm

Image distance : 10 cm

To find :

The focal length of the mirror.

Solution :

Using the mirror formula that is,

» A formula which gives the relationship between image distance, object distance and focal length of a sperical mirror is known as the mirror formula .i.e.,

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

where,

• v denotes Image distance
• u denotes object distance
• f denotes focal length

By substituting all the given values in the formula,

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

$\dashrightarrow\sf \dfrac{1}{10} + \dfrac{1}{ - 20} = \dfrac{1}{f}$

$\dashrightarrow\sf \dfrac{1}{10} - \dfrac{1}{20} = \dfrac{1}{f}$

$\dashrightarrow\sf \dfrac{2 - 1}{20} = \dfrac{1}{f}$

$\dashrightarrow\sf \dfrac{1}{20} = \dfrac{1}{f}$

$\dashrightarrow\sf f = 20 \: cm$

Thus, the focal length of the mirror is 20 cm.