Question

How do you verify experimentally that the angle of refraction is more than angle of incidence when light rays travel from denser to rarer medium? 

(OR) 

When the light rays travel from denser to rarer medium, how can you explain, the angle of refraction is more than angle of incidence experimentally?

Answer 1

Procedure :

• Take a metal disc. Use a protractor and mark angles along its edge as shown in the figure. 
• Arrange two straws at the centre of the disc, in such a way that they can be rotated freely about the centre of the disc. 
• Adjust one of the straws to make an angle 10°. 
• Immerse half of the disc vertically into the water, filled in a transparent vessel. While dipping, verify that the straw at 10° must be inside the water. 
• From the top of the vessel, try to view the straw which is inside the water as shown in the figure. 
• Then adjust the other straw which is outside of the water until both straws look like they are in a single straight line. 
• Then take the disc out of the water and observe the two straws on it. You will find that they are not in a single straight line. 
• Measure the angle between the normal and second straw. Note the values in the following table.

i	r	sin i	sin r	sin i/ sin r
10°
15°
20°
25°
30°
35°
40°
45°

• Do the same for various angles and find the corresponding angles of refraction and note them in the table. 

Observation : 

We will find the angle of refraction is more than angle of incidence. i. e., r > i. 

Conclusion : 

When light travels from denser (water) to rarer (air) it bends away from the normal.