Question

Two plane mirrors are parallel to each other and spaced 20 cm apart. A luminous point is placed between them at a distance 5 cm from one mirror. Determine the distances of the first nearest images from each other.

• A. 70
• B. 10
• C. 40
• D. 35

Answer 1

Answer: (C)

Given: Two plane mirrors placed at 20 cm apart. A luminous point is placed between them at a distance 5 cm from one mirror.

To find the distances of the first nearest images from each other.

Solution:

As the point is placed at distance 5 cm from one mirror, the first image formed by first mirror at a distance of 5 cm.

As the luminous point is 5 cm from one mirror it will be at a distance of 15 cm from other mirror. Hence the first image formed by second mirror will be formed behind the second mirror at a distance of 15 cm.

Hence the the distances of the first nearest images from each other will be 40 cm (15+15+5+5 = 40 cm), as shown in above figure.