Question

A concave mirror of focal length 20 cm produces an image twice the height of the objectifs
image is real, then the distance of the object from the mirror is
(1) 20 cm
(2) 60 cm
(3) 10 cm
(4)30cm
​

Answer 1

Answer:

hi/ho =2

-v/u = hi/ho = 2

-v= 2u

1/f = 1/u + 1/ v

1/f = 1/-2u + 1/u

1/f = 3/ 2u

f = 2u/3= -20 cm

u= -30 cm

option: (4)

Answer 2

Answer:

a concave mirror produces an image twice the height of the object i,.e h1/h2=2.

Focal length=20cm

We have to find the distance of object from the mirror.

m=h1/h2=2

-v/u=2

-v=2u

so, we apply mirror formula

1/f=1/v+1/u

1/f=2u/3

2u/3=-20

u=-30cm

option 4is correct.

HOPE IT WILL HELP YOU ☺️