Question

How do you verify experimentally that $\frac{\sin i}{\sin r}$ is a constant?

Answer 1

Aim: Obtaining a relation between angle of incidence and angle of refraction

Materials required: A plank, white chart, protractor, scale, small black painted plank, a semi circular glass disc of thickness nearly 2 cm, pencil and laser light

Procedure: Take a wooden plank which is covered with white chart. Draw two perpendicular lines, passing through the middle of the paper as shown in figure. Let the point of intersection be O. Mark one line as NN which is normal to another line marked as MM. Here MM represents the line drawn along the interface of two media and NN represents the normal drawn to this line at 'O'.

Take a protractor and place it along NN in such a way that its centers coincides with 'O' as shown in figure. Then mark the angles from $0^{\circ }$ to ${90}^{\circ }$ on both sides of the line NN as shown in the figure. Repeat the same on the other side of the line NN. The angles should be indicated on the curved line.

Now place a semi-circular glass disc so that its diameter coincides with the inter face line (MM) and its center coincides with the point 'O'.

Send laser light along a line which marks ${15}^{\circ }$ with NN. Measure its corresponding angle of refraction. Repeat the experiment for ${20}^{\circ },{30}^{\circ },{40}^{\circ },{50}^{\circ }$ and ${60}^{\circ }$ and noted the corresponding angles of refraction.

If we calculate $\sin i,\sin r$ ratio we will get the ratio as constant.