Question

An image is formed 5cm behind a convex mirror of focal length 10cm . At what distance is the object placed from the mirror.

Answer 1

for mirror
1/v+1/u=1/f
1/(-5)+1/u=1/10
1/u=15/50
u=10/3cm infront of mirror

Answer 2

Object distance U = -5 cm(to the left of mirror)

Image distance V = ?

Focal length f = 10 cm(convex mirror)

By using the mirror formula we have

1/V + 1 / U = 1/f

1/V + 1/-5 = 1/10

1 / V = 1/10 + 1/5

1/V = 3/10 or V = 10/3

V = +3.33cm

Position of the image is at a distance of 3.33 cm from the convex mirror on its right side(behind the mirror). Since the image is formed behind the convex mirror, therefore the nature of image is virtual and erect.

Magnification m = - V/U

So m = - (3.33)/-5

m = +0.66