Explain why a red apple appears red when viewed in white light, and state what colour the same apple would appear when viewed in green light only.

Eduqas GCSE Physics — 6.4 Colour and frequency · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

White light is made up of all the colours of the visible spectrum. Objects appear coloured because of the way they absorb and reflect different colours of light.

Model answer (4 marks)

White light contains all colours of the visible spectrum.
The apple absorbs all colours of light except red, so it reflects only red light.
The reflected red light reaches our eyes, making the apple appear red.
In green light only the apple absorbs the green light and reflects none, so it would appear black.

Examiner tips

Use the word "absorbs" and "reflects" to show understanding of colour perception.
Mention that white light contains all visible wavelengths.
State the colour change in green light explicitly.
Keep the answer concise and to the point.

Common mistakes

Saying the apple *emits* red light instead of reflecting it.
Confusing the apple’s colour with the colour of the light source.
Using vague terms like "looks red" without explaining absorption/reflectance.

Mark scheme (4 marks)

White light contains all colours of the visible spectrum (or all frequencies/wavelengths of visible light)
The apple absorbs all colours of light except red (absorbs all other colours/frequencies)
The apple reflects red light into our eyes (so we see it as red)
In green light only, the apple would appear black (because it absorbs green light and has no red light to reflect)

Key terms in this question

white light