IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

# Verification of the Laws of Reflection

## Introduction

The laws of reflection are,

• The incident ray, reflected ray, and normal to the surface lies in the same plane.
• The angle of incidence $$i$$ is equal to the angle of reflection $$r$$.

## Apparatus

A plane mirrors, scale, protractor, thermocol sheet, white paper, pins.

## Procedure

1. Fix the white paper on the thermocol sheet with the help of pins.
2. Place the mirror near to one edge of the paper and mark its position.
3. Place two pins vertically on one side of the normal so that line joining two pins make an angle of approximately 30 degree with the normal.
4. See image of two pins from other side of the normal and place a pin vertically so that it is in line with images of other two pins. Similarly, place one more pin at some distance from this pin.
5. Extend the lines. Measure angle of incidence and angle of reflection.
6. Repeat for two more incident angles (say 45 degree and 60 degree).
7. Now, see the head of the pins in step (3). Raise one of the pin and press another pin. Now repeat step (4) such that images of the pin-head are aligned. Visualise the plane containing incident ray, reflected ray and normal. You may place a paper on this plane. Raise another pin and visualize again.

## Discussion

Write the results in the form of a table.