Question

\(\text{ Light is incident on an interface between water } (\mu = \frac{4}{3}) \text{ and glass } (\mu = \frac{3}{2}).\\\) \(\text{For total internal reflection, light should be traveling from:}\)

• A. \(\quad \text{water to glass and } \angle i > \angle i_c \\\)
• B. \(\quad \text{water to glass and } \angle i < \angle i_c \\\)
• C. \(\quad \text{glass to water and } \angle i < \angle i_c \\\)
• D. \(\quad \text{glass to water and } \angle i > \angle i_c\)

Answer 1

The Correct Option is D

Given refractive indices:

• Water (μ_w) = 4/3 ≈ 1.33
• Glass (μ_g) = 3/2 = 1.5

Conditions for total internal reflection (TIR):

1. Light must travel from denser to rarer medium (μ_incident > μ_refracted)
2. Angle of incidence must be greater than critical angle (∠i > ∠i₀)

Critical angle calculation:

sin i₀ = μ_rarer/μ_denser = μ_w/μ_g = (4/3)/(3/2) = 8/9

Since μ_g (1.5) > μ_w (1.33):

• TIR occurs when light travels from glass to water
• And when ∠i > sin^-1(8/9)

Therefore, the correct condition is:

(4) glass to water and ∠i > ∠i₀

Answer 2

\(\text{Total internal reflection occurs when light travels.}\)

\(\text{From a denser medium to a rarer medium and the angle of incidence exceeds the critical angle.}\)

\(\\ \text{Here, glass } (\mu = \frac{3}{2}) \text{ is denser than water } (\mu = \frac{4}{3}). \text{ So, for total internal reflection, the light should be traveling from glass to water}\\ \text{and the angle of incidence should be greater than the critical angle } \angle i_c.\)