A artist paints a picture using yellow paint and blue paint mixed together. Explain, in terms of colour absorption and reflection, why the mixed paint appears green when viewed in white light.

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).

Model answer (4 marks)

White light contains all visible wavelengths (red, green, blue). Yellow paint absorbs blue light and reflects red and green. Blue paint absorbs red light and reflects blue and green. Only green light is reflected by both paints, so the mixture reflects only green, which is seen.

Examiner tips

  • Use the word ‘reflects’ and ‘absorbs’ clearly; mention white light contains all colours.
  • Show the chain of reasoning: yellow absorbs blue, blue absorbs red, only green common.
  • Keep answer concise to fit 4 marks.
  • Use UK spelling (colour).

Common mistakes

  • Confusing ‘reflects’ with ‘absorbs’ for each paint.
  • Forgetting to state that white light contains all colours.
  • Over‑expanding the answer with unnecessary detail.

Mark scheme (4 marks)

  1. White light contains all colours of the visible spectrum (or contains red, green and blue light)
  2. Yellow paint absorbs blue light and reflects red and green light
  3. Blue paint absorbs red light and reflects blue and green light
  4. Only green light is reflected by both paints, so green is the only colour reflected by the mixture

Key terms in this question

absorption · reflection · white light

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