Question

What is the focal length of a concave mirror which forms a real image at 4 m of an object placed 2 metres from the concave mirror?​

Answer 1

Answer:

Focal length will be -133.33 cm

Explanation:

u= -200com

v= -400cm

1/f= 3/-400 =

f=-133.33

Answer 2

Mirror is a concave mirror, So

u = - 2m ( Object is always placed on the left side of the mirror, So it's negative )

v = - 4m ( Image is not virtual , given in the question)

Through , Mirror formula.

1/f = 1/v + 1/u

1/f = -1/4 - 1/2

1/f = -2 - 1/4

1/f = -3/4

f = -4/3 m.