Question

The incorrect statement about refractive index for a pair of media is

• A. It depends upon nature of the first medium
• B. It depends upon nature of the second medium
• C. It depends upon wavelength of light
• D. It depends upon angle of incidence

Hint:

Refractive index is a material property. Just as the density of a substance doesn't change regardless of its mass, the refractive index doesn't change regardless of the angle at which light strikes it.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify which factor does NOT determine the refractive index of a pair of media.
Step 3: Detailed Explanation:
The relative refractive index (\(n_{21}\)) for light traveling from medium 1 to medium 2 is a characteristic physical property of that pair of substances for a given wavelength. It is defined as the ratio of the speed of light in medium 1 to the speed of light in medium 2.
- Nature of media: Since speed of light varies in different substances (vacuum, water, glass, etc.), the refractive index inherently depends on the nature of both the first and second media.
- Wavelength of light: According to Cauchy's equation, refractive index decreases as wavelength increases (\(n \approx A + \frac{B}{\lambda^2}\)). Thus, it depends on the color/wavelength of light.
- Angle of incidence: While Snell's law states that \(n = \frac{\sin i}{\sin r}\), this ratio is a constant for the given media and wavelength. Changing the angle of incidence (\(i\)) will change the angle of refraction (\(r\)) accordingly, but the value of the refractive index itself remains unchanged.
Therefore, statement (4) is incorrect.
Step 4: Final Answer:
The incorrect statement is (4).