Which of the following cases cannot produce total internal reflection? A light ray travelling from

Analyze the question: We need the case where total internal reflection (TIR) is impossible.

Concept: Total internal reflection happens only when:

1. Light travels from a denser (higher refractive index) medium to a less dense (lower refractive index) medium, and
2. The angle of incidence is greater than the critical angle, where sin C = n₂/n₁ (with n₁ > n₂).

If light goes from a less dense to a denser medium, it bends towards the normal. There is no critical angle, so TIR cannot occur.

Check each option:

• A. Glass to water: n(glass) ≈ 1.5 and n(water) ≈ 1.33. Light goes from denser to less dense, so TIR is possible.
• B. Kerosene to air: n(kerosene) ≈ 1.44 and n(air) ≈ 1.0. Denser to less dense, so TIR is possible.
• C. Air to water: n(air) = 1.0 and n(water) ≈ 1.33. Light goes from less dense to denser, so TIR is impossible.
• D. Water to ice: n(water) ≈ 1.33 and n(ice) ≈ 1.31. Water is slightly denser optically than ice, so light goes from higher to slightly lower refractive index. TIR is possible, though only at a very large critical angle (about 80°).

Answer: Air to water is the only case where light enters a denser medium, so it cannot produce total internal reflection.

Tip: Remember "Denser to Rarer" (dense to rare) for TIR. If the light is going into a denser medium, TIR is never possible, so look for the option where light starts in the less dense medium, often air.