Write an experiment to trace the …

Procedure

1. Fix a white sheet on a drawing board using drawing pins.
2. Place the triangular prism resting on its triangular base. Using a pencil, draw the outline of the prism.
3. Draw NEN normal to the face of the prism AB. make an angle between 30° and 60°.
4. On the line PE, fix two pins at a distance of 5cm from each other and mark these as P and Q.
5. Look for the images of the pins at P and Q through the other face of the prism AC.
6. Fix two pins at R and S such that they appear as a straight line as that of the P and Q when it is viewed from AC face of the prism.
7. Remove the pins and the prism.
8. At point F, make the points R and S meet by extending them.
9. PQE is the incident ray which is extended till it meets face AC. SRF is the emergent ray which is extended backward to meet at point G.
10. Now mark the angle of incidence ∠i, angle of refraction ∠r and the angle of emergence ∠e and ∠D as shown in the experimental setup.
11. Repeat the experiment for more angles between 30° and 60°.

Observations

1. At surface AB, the light ray enters and bends towards the normal on refraction.
2. At surface AC, the light ray bends away from the normal as it travels from one medium (glass) to the other (air).
3. The angle of deviation is observed. Here, the emergent ray bends at an angle towards the direction of the incident ray.

Conclusion

1. The incident ray bends towards the normal when it enters the prism and while leaving the prism it bends away from the normal.
2. With the increase in the angle of incidence, the angle of deviation decreases. After attaining the minimum value, it increases with an increase in the angle of incidence.