NCERT Solutions for Class 8 Science Chapter 13

Important NCERT Questions

8th Chapter 13 Light

NCERT Books for Session 2023-2024

CBSE Board and State Board

Questions No: 14

Description:

A plane mirror is a flat, smooth reflecting surface that reflects light without distortion. It forms images by regular reflection, maintaining the same size as the object, with left-right reversal. These mirrors produce virtual images located behind the mirror, widely used in daily applications, such as in bathrooms and dressing rooms.

When a candle is placed between two parallel plane mirrors, multiple images can be formed due to the phenomenon of multiple reflections. The number of images formed can be calculated using the formula:

Number of Images = 360°/(angle between mirrors – 360°)

For parallel mirrors, the angle between the mirrors is twice the angle formed between one of the mirrors and the line perpendicular to them.

Given that the distance between the mirrors is 40 cm, and they are parallel, we need to find the angle between the mirrors. Using trigonometry:

tan θ = (distance between mirrors)/(length of mirror)

tan θ = (40 cm)/(length of mirror)

θ = tan⁻¹ ((40cm)/(length of mirror))

The angle between the mirrors (and consequently the angle of each image) depends on the length of the mirror, which is not specified. Without the specific length of the mirrors, the exact number of images formed cannot be determined.

However, in theory, for an infinite length of mirrors and an angle between them calculated from the given distance, an infinite number of images would be formed. In practical scenarios with finite mirrors, the number of images formed would be significantly large but finite.