# A student shines a beam of white light onto a green opaque surface. Explain why the surface appears green when viewed in white light, and describe what would happen to the appearance of the surface if it were viewed under red light only.

> Edexcel A-Level Physics (9PH0) — 5.1 Wave properties · Explain · 5 marks

> White light is made up of all the colours of the visible spectrum. Opaque materials absorb some wavelengths and reflect others.

## Mark scheme (5 marks)

1. The green surface absorbs all colours/wavelengths of white light except green
2. Only green light is reflected from the surface
3. Our eyes detect the reflected green light, so the surface appears green
4. Under red light only, the green surface absorbs the red light / no green light is present to be reflected
5. The surface appears black under red light because no light is reflected to the observer

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-shines-a-beam-of-c1ff8b88) · Published by Druglandscape Ltd.