Question

a 5 cm tall object is placed at a distance of 20cm from a concave mirror of focal length 30 cm. use mirror formula to determine the position and size of the image formed​

Answer 1

height of object=5cm
u=-20cm
f= -30cm

Answer 2

Answer: The image is virtual and height of the image is 15 cm.

Explanation:

Given that,

Height of the object h = 5 cm

Distance of the object u = -20 cm

Focal length f = -30 cm

Using mirror's formula

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

$\dfrac{1}{-30}=\dfrac{1}{v}+\dfrac{1}{-20}$

$\dfrac{1}{v}= \dfrac{1}{60}$

$v = 60 cm$

The image is formed at 60 cm on the back side of the mirror.

The height of the image is

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

$\dfrac{h'}{5}=-\dfrac{60}{-20}$

$h' = 15 cm$

Hence, The image is virtual and height of the image is 15 cm.