Science (086) — AI-generated practice question

(i) Optically denser medium:
Medium A is optically denser because the speed of light in it (2.0 × 10⁸ m/s) is lower. A medium in which light travels slower has a higher refractive index and is optically denser.

(ii) Refractive index of medium A with respect to medium B:

$$n_{AB} = \frac{\text{Speed of light in medium B}}{\text{Speed of light in medium A}} = \frac{v_B}{v_A} = \frac{2.5 \times 10^8}{2.0 \times 10^8} = 1.25$$

(iii) Direction of bending:
The ray travels from medium B (rarer) into medium A (denser). Therefore, it bends towards the normal at the interface.

Source: Chapter 9, Section 9.3.2 – The Refractive Index

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• Optically denser = lower speed of light = higher refractive index. Always link these three together.
• For $n_{AB}$ (A with respect to B), use the formula: speed in B ÷ speed in A (i.e., speed of the second medium in the numerator when naming is "first w.r.t. second" — follow Eq. 9.6 pattern carefully).
• Bending direction rule: rarer → denser = bends towards normal; denser → rarer = bends away from normal. Examiners expect this stated explicitly.