#### Question

A convex lens produces an inverted image magnified three times of an object placed at a distance of 15 cm from it. Calculate focal length of the lens.

#### Solution

Given:

Object distance, *u *=-15 cm

Magnification, *m *=-3 (Image is inverted.)

Applying magnification formula, we get:*m* = *v*/*u* =-3

or, *v*/(-15) = -3

or, *v* = 45 cm

Applying lens formula, we get:

1/*v -* 1/*u *= 1/*f*

1/45- 1/(-15) = 1/*f*

1/*f* = ( 1+3 )/45

1/*f* = 4/45

or *f *= 11.2 cm

Hence, focal length of the lens is 11.2 cm.

Is there an error in this question or solution?

Solution A Convex Lens Produces an Inverted Image Magnified Three Times of an Object Placed at a Distance of 15 Cm from It. Calculate Focal Length of the Lens. Concept: Refraction of Light - Image Formation by Lenses - Convex Lens.