Light is made to travel from medium 1 to medium 3 through medium 2 as shown in figure. If μ1, μ2 and μ3 are the refractive indices of first, second and third media and i2 > i1, then
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When light travels through multiple media, Snell's Law applies at each interface. Given i₂ > i₁, the angle in medium 2 is larger than in medium 1. Snell's Law states: μ₁ sin i₁ = μ₂ sin r₁ and μ₂ sin i₂ = μ₃ sin r₂. Since i₂ > i₁ and the path is symmetric, r₁ = i₂. Therefore, sin i₁ < sin i₂ implies μ₂ > μ₁. Similarly, for the second interface, μ₂ > μ₃. Thus, the refractive index decreases: μ₁ < μ₂ > μ₃. This means 1μ₃ < 3μ₁ is correct, as light bends away normal entering a rarer medium.
Final answer: 1μ3 < 3μ1