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

Answer 1

Given,M= -3 ( because image formed is real and inverted)and u=-15cm

This gives -3=v/u

-3u=v

-3*-15=v

45cm =v

By applying lens formula

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

1/f= 1/45+1/15

1/f= 4/45

F= 45/4 cm