Question

Find the position of the image formed in convex mirror of focal length 12 cm when object is placed at the distance of (i) 8 cm, (ii) 12 cm and (iii) 18 cm from the mirror

Answer 1

4.8 cm, 6 cm and 7.2 cm

Explanation:

From the mirror formula we get,

1/f = 1/u + 1/v

Where f is the focal length, u is the distance of the object and v is the distance of the image.

Given f = 12 cm

Let’s find position of the image formed using the above formula.

1) u = - 8 cm

1/12 = 1/8 + 1/v

1/v = 1/12 – 1/(-8)

     = 1/12 + 1/8

     = 5/24

Hence v = 24/5 = 4.8 cm.

The image will be formed at a distance of 4.8 cm to the right side of the pole.

2) u = - 12 cm

1/v = 1/f – 1/u

= 1/12 – 1/(-12)  

= 2/12

V = 12/2 = 6 cm

3) u = - 18 cm

1/v = 1/f – 1/u

= 1/12 – 1/(-18)

= 5/36

V = 36/5 = 7.2 cm