Question

Find the image distance when an object is kept 60 cm. From the pole of a concave mirror having 20 cm . focal length

Answer 1

focal length will be negative 30 cm

Answer 2

Given,

Object distance from the mirror=60cm,

Focal length of the mirror=20cm

To Find,

Image distance from the mirror.

Solution,

Object is placed 60 cm from the mirror.

means, u = -60 cm

Focal length of the concave mirror is 20 cm.

Means, f = -20 cm

We have the mirror formula,

1/f = 1/v + 1/u

⇒-1/20 = 1/v- 1/60

⇒-1/20 + 1/60 =1/v

⇒v = -30 cm

Hence, image distance from the mirror is 30cm.