# A ray of light travels from glass into air and hits the boundary at a large angle to the normal. Explain why the ray does not pass into the air.

> Eduqas GCSE Physics — 5.2 Waves at material interfaces · Explain · 4 marks

> Light can travel through both glass and air. When light reaches the boundary between the two materials, different things can happen depending on the angle at which it hits the boundary.

## Mark scheme (4 marks)

1. The angle of incidence is greater than (or equal to) the critical angle
2. Total internal reflection occurs
3. The light is reflected back into the glass (not transmitted into the air)
4. This occurs because light travels from a denser medium (glass) into a less dense medium (air)

## Key terms

- [boundary](https://www.gradenine.co.uk/glossary/boundary)

## Related

- [Revision notes for Eduqas GCSE Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-ray-of-light-travels-from-782cf73e) · Published by Druglandscape Ltd.