Understanding Refraction and Refractive Index

Let's analyze the given statements about refraction and the refractive index to determine which one is correct.

Analyzing Statement I: Refraction and Speed of Light

Statement I says: Refraction is due to the change in the speed of light when it enters from one transparent medium to another.

• Refraction is a phenomenon where light bends as it passes from one transparent medium to another.
• Examples of transparent media include air, water, and glass.
• The speed at which light travels is different in different transparent media. Light travels fastest in a vacuum, slightly slower in air, even slower in water, and slower still in glass.
• When light moves from a medium where it travels faster (like air) to a medium where it travels slower (like water or glass), it bends towards the normal.
• When light moves from a medium where it travels slower to one where it travels faster, it bends away from the normal.
• This change in direction, or bending of light (refraction), is a direct consequence of the change in the speed of light as it crosses the boundary between the two media.

Therefore, statement I is correct. Refraction is indeed caused by the change in the speed of light.

Analyzing Statement II: Refractive Index of Water

Statement II says: The refractive index of water is 1.33.

• The refractive index (μ or n) of a medium is a measure of how much the speed of light is reduced in that medium compared to the speed of light in a vacuum.
• It is defined by the formula: $$\mu = \frac{\text{Speed of light in vacuum (c)}}{\text{Speed of light in the medium (v)}}$$
• The refractive index is a dimensionless quantity.
• The refractive index of water is a well-established value in physics. The approximate value for the refractive index of water at room temperature and visible light wavelengths is indeed around 1.33. This means that light travels approximately 1.33 times slower in water than in a vacuum.

Therefore, statement II is also correct. The refractive index of water is approximately 1.33.

Conclusion

Based on the analysis of both statements:

• Statement I about the cause of refraction is correct.
• Statement II about the refractive index of water is correct.

Since both statements are correct, the option that states "Both I and II" is the correct choice.