When a ray of light travels obliquely from air into water, does it bend towards or away from the normal? Give a reason for your answer.
Generated by claude-sonnet-4-6 · 2026-06-26 01:10 · grounding rag
Model Answer
When a ray of light travels obliquely from air into water, it bends towards the normal.
Reason: Water is optically denser than air (refractive index of water = 1.33). When light travels from a rarer medium (air) to a denser medium (water), it slows down and bends towards the normal.
Source: Chapter 9, Section 9.3.2 – The Refractive Index
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Explanation
- The key concept here is rarer to denser = bends towards normal; denser to rarer = bends away from normal.
- Always link the bending direction to the change in speed: slower speed in denser medium causes the ray to bend towards the normal.
- Mentioning the refractive index value (1.33 for water) adds a precise touch but is not compulsory for 2 marks.
- The examiner awards 1 mark for the correct direction and 1 mark for a valid reason.