Question

In refraction, light waves are bent on passing from one medium to second medium because, in the second medium.

• A. frequency is different
• B. speed is different
• C. coefficient of elasticity is different
• D. amplitude is smaller

Answer 1

The Correct Option is B

Let's analyze each option to understand why light waves bend during refraction.

1. Frequency is different:

The frequency of a light wave is determined by the source of the light and remains constant when light travels from one medium to another. If the frequency were to change, it would imply a change in the fundamental nature of the light itself. Refraction is a phenomenon at the boundary of two media and does not alter the source's frequency. Hence, the frequency of light remains unchanged during refraction.

2. Speed is different:

Refraction is fundamentally caused by the change in the speed of light as it passes from one medium to another. The refractive index of a medium is defined as the ratio of the speed of light in vacuum to the speed of light in that medium ($n = c/v$). When light enters a medium with a different refractive index, its speed changes. This change in speed at the boundary between two media leads to the bending of the light wave. This is the correct explanation for refraction.

3. Coefficient of elasticity is different:

The coefficient of elasticity is a mechanical property of a medium, related to its ability to deform under stress and return to its original shape. While media have different elastic properties, this is not the primary reason for the refraction of light. Refraction is an electromagnetic phenomenon, governed by the interaction of light with the electromagnetic properties of the medium (like permittivity and permeability), not its mechanical elasticity.

4. Amplitude is smaller:

When light passes from one medium to another, some portion of it may be reflected and some is transmitted. The amplitude of the transmitted light can be smaller than the incident light because some energy is lost due to reflection or absorption. However, a change in amplitude alone does not cause the bending of light. Amplitude relates to the intensity or brightness of light, not the direction of its propagation in refraction. The bending is caused by the change in speed.

Conclusion:

The bending of light waves during refraction is primarily due to the change in the speed of light as it moves from one medium to another. This change in speed causes different parts of the wavefront to travel different distances in the same time, resulting in a change in the direction of propagation.

Final Answer: The final answer is speed is different

Answer 2

(A) frequency is different: Incorrect. Frequency remains constant during refraction.

(B) speed is different: Correct. The speed of light changes when it enters a different medium, which causes the bending of light (refraction).

(C) coefficient of elasticity is different: Incorrect. This relates to mechanical waves, not electromagnetic waves.

(D) amplitude is smaller: Incorrect. While the amplitude may decrease slightly due to some reflection and absorption, this is not the primary reason for refraction.

The correct answer is (B): speed is different