Question

When the path of a light ray refracted through a glass prism is reversed, how will the angle of deviation change? Explain.

Hint:

Reversibility of light → Same path → Same angle of deviation.

Answer 1

Effect on Angle of Deviation When the Path of Light is Reversed Through a Prism

When the path of a light ray refracted through a glass prism is reversed, the angle of deviation remains the same.

Explanation:

1. Principle of Reversibility of Light:
Light follows the same path if its direction is reversed. This is known as the principle of reversibility of light.

2. Refraction at Both Surfaces:
In a prism, refraction occurs at two surfaces. When the ray is reversed, the emergent ray becomes the incident ray and retraces the same path inside the prism.

3. Same Angles are Formed:
The angles of incidence and refraction interchange, but their values remain the same according to Snell’s law.

4. Angle of Deviation:
Since the geometry of the prism and the refractive index remain unchanged, the total deviation of the ray from its original path remains equal in both forward and reversed directions.

Conclusion:
When the path of a light ray through a glass prism is reversed, the angle of deviation does not change. It remains the same due to the principle of reversibility of light.