GKFix MCQ Question

What is the refractive index of medium 3 with respect to medium 1 if n₃₂ and n₂₁ are known?

• A. n₃₁ = n₃₂ + n₂₁
• B. n₃₁ = n₃₂ − n₂₁
• C. n₃₁ = n₃₂ × n₂₁
• D. n₃₁ = n₂₁ / n₃₂