Question

A convex lens of focal length 20 cm is used to form the image of an object placed 30 cm away from the lens. Find the position and nature of the image formed.

Answer 1

Given: Focal length (f) = +20 cm

Object distance (u) = −30 cm

Formula: `1/v - 1/u = 1/f`

`1/v - 1/(-30) = 1/20`

`1/v + 1/30 = 1/20`

`1/v = 1/20 - 1/30`

`1/v = (3 - 2)/60`

`1/v = 1/60`

v = + 60 cm

Magnification (m) = `v/u`

= `60/(-30)`

= −2