Question

The colour which has the highest critical angle of incidence is

• A. Violet
• B. Red
• C. Yellow
• D. Green

Hint:

Longer wavelengths (like red) have higher critical angles due to lower refractive indices.

Answer 1

The Correct Option is B

Critical angle $C$ is given by $\sin C = \dfrac{1}{\mu}$, where $\mu$ is the refractive index.
Higher the wavelength of light, lower the refractive index, and hence higher the critical angle.
Among visible light, red light has the longest wavelength (≈700 nm) and thus the lowest refractive index.
Therefore, red has the highest critical angle of incidence.