Question

An object 4cm high is placed 40 cm from a concave mirror of focal length20 cm find the distance from the mirror at which a screen

Answer 1

Hope it help you

if you have more Question of mirror please add

thanks for question

Answer 2

Answer:

The distance of the image at 40 cm from the mirror and the image is inverted.

Explanation:

Given that,

Height of the object h = 4 cm

Distance of the object u = -40 cm

Focal length f = - 20 cm

Using mirror's formula

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

$\dfrac{1}{-20}=\dfrac{1}{v}+\dfrac{1}{-40}$

$\dfrac{1}{v}=-\dfrac{1}{40}$

$v = -40\ cm$

The distance of the image is 40 cm.

The magnification is

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

$m =\dfrac{40}{40}$

$m=-1$

We know that,

$m=\dfrac{h'}{h}$

$-1=\dfrac{h'}{h}$

$h' = -4\ cm$

Hence, The distance of the image at 40 cm from the mirror and the image is inverted.