ICSE Class 9 Answered

When a light ray strikes a plane mirror, the light ray reflects off the mirror.

Reflection involves a change in direction of the light ray.

The angle of incidence is the angle between this normal line and the incident ray.

The angle of reflection is the angle between this normal line and the reflected ray.

According to the law of reflection, the angle of incidence equals the angle of reflection.

Also, the incident ray, reflected ray and the normal at the point of incidence lie in the same plane.

Experiment

Aim :- To prove the law of reflection through a plane mirror.

Apparatus :- Soft board, white sheet of paper , optical pins , mirror , pencil, protactor and ruler .

Procedure :- 

1- Place the paper on the board and fix 

2- Place the mirror vertically on the white sheet of paper and trace its edge.

3- Draw a line at right angles to the edge of the edge of the mirror to act as the normal- ON .

4- Stating with angle i as 30 degree , draw an incident ray and place two pins, P and Q along it as shown

5- With your eyes at position shown, place two other pins R and S to coincide with the images of P and Q as seen in the mirror

6- Remove pins R and S and join the dots left with a straight line

7-Measure and record angle r.

8- Repeat procedure 4,5,6 and 7for angles i = 35 degree, 40 degree, 45 degree, 50 degree and 55 degree.

9- Record the results in a table.

Observation:-

1-The angle of incidence equals the angle of reflection.

2- Incident ray, Reflected ray and the normal at the point of incidence lie in the same plane.

Hence the laws of reflection proved.