Question

The focal length of a concave mirror is 12 cm.
Where should an object of length 4 cm be placed,
so that a real image of 1 cm length is formed?
(1) 48cm
(2) 3cm
(3) 60 cm
(4) 15 cm​

Answer 1

Explanation:

f=-12cm

hi=1cm

ho=4cm

hi/ho=1/4

1/4=-v/u

v=-u/4

according to mirror formula

1/u +1/v=1/ f

1/u-4/u=1/12

(1-4)/u=1/12

-3/u=1/12

u=-48cm

object should be placed 48 CM away from the mirror.

THANKS!!!

Answer 2

Question:- The focal length of a concave mirror is 12 centimetre where should an object of length 4 cm be placed so that a real image of 1 cm length is formed .

Answer:- Given that,

Focal length of a concave mirror f=12cm

Object length h=4

Real image length h =1cm

We know that,

m = −v/u = −f / -f -(u)

-1 / u = −12 / −12 - u Option (3) 60 cm

12+u=−48

u=−48−12

u=−60cm

Hence, the object distance is 60 cm

Answer:-