Question

focal length of concave lens is 30cm. inage diatance is 90cm and what is the object distance​

Answer 1

Answer:

f = -30 (since concave mirror)

v = 90

u= ?

So using mirror formula

1/f = 1/u + 1/v

1/f - 1/v = 1/u

1/u = 1/(-30) - 1/90

1/u = [(-3) - (1)] / 90

1/u = -4 / 90 = 1/22.5

u = -22.5

So Object distance = 22.5 cm

Answer 2

Answer:

Object didtance should be 22.5 cm