Question

a)
If the Image formed by a convex mirror is one third of the
object length. When it is placed at 40 cm distance from the
mirror then the focal length of mirror will be:-
1
i) 10 cm
ii) 20 cm
ii) 30 cm
iv) 40 cm​

Answer 1

Explanation:

It will be 30 cm ok plz mark me as BRAINLIEST.

Answer 2

Answer:

The focal length of mirror is 10cm.

Explanation:

Given that image formed by a convex mirror is one third of the object length.

If L is the length of object then image length is $\frac{L}{3}$.

Object distance, $u=40cm$

We need to find the focal length of the mirror.

The distance between the center of a lens or curved mirror and its focus is called focal length.

From mirror formula we know that $\frac{1}{f} =\frac{1}{v}+\frac{1}{u}$

Magnification, $m=-\frac{v}{u}$

Here magnification is $-\frac{1}{3}$ as the image length is one third of the object length.

Substituting in m gives: $-\frac{1}{3} =-\frac{v}{u}$

$\frac{1}{3} =\frac{v}{40}$

$v=\frac{40}{3}$

Substituting in mirror formula

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

$\frac{1}{f} =\frac{1}{\frac{40}{3} }+\frac{1}{-40}$

$\frac{1}{f} =\frac{3}{40}+\frac{1}{40}$

$\frac{1}{f} =\frac{4}{40}$

$\frac{1}{f} =\frac{1}{10}$

$f=10cm$

The focal length of the mirror is 10cm.

To know more about focal length go to the following link.

brainly.in/question/54230672

To know more about mirror go to the following link.

brainly.in/question/7267709

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