Question

The focal length of a concave lens is 40 cm. If an object is kept at a distance of 60 cm from the lens, find out the distance of the image formed.

• A. +20 cm
• B. +24cm
• C. -20 cm
• D. -24 cm

Answer 1

The correct option is D -24 cm

Focal length (f) = -40 cm
Object distance (u) = -60 cm
Image distance (v) = ?
Lens formula,
1/f = 1/v - 1/u
1/v = 1/f + 1/u = 1/(-40) + 1/(-60) = -5/120
v = -120/5 = -24 cm