Explain why different objects appear different colours when white light shines on them, and describe what happens when white light passes through a colour filter.
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. When white light interacts with objects and materials, the colours we see depend on how the light is absorbed or reflected.
Model answer (5 marks)
Objects appear coloured because the light they reflect has a particular frequency: a coloured object reflects light of its own colour and absorbs all other frequencies, whereas a white object reflects all frequencies.
When white light passes through a colour filter, the filter only transmits light of a single frequency (its own colour) and absorbs all other frequencies, so the transmitted light is that single colour.
When white light passes through a colour filter, the filter only transmits light of a single frequency (its own colour) and absorbs all other frequencies, so the transmitted light is that single colour.
Examiner tips
- Use the term "frequency" or "wavelength" when describing reflected light.
- Show the two processes: reflection/absorption for objects, transmission/absorption for filters.
- Mention that white light contains all visible frequencies.
- Keep the answer concise to fit the 5‑mark limit.
Common mistakes
- Confusing reflected light with transmitted light for objects.
- Saying the filter *adds* colour instead of transmitting only one colour.
- Using vague terms like "colourful" instead of specifying frequency or wavelength.
Mark scheme (5 marks)
- The colour of an object is determined by the frequency of light reflected from it
- A coloured object reflects its own colour and absorbs all other colours
- A white object reflects all colours / frequencies of light
- A colour filter only allows light of a single colour (single frequency) to pass through
- The filter absorbs all other colours / frequencies of light
Key terms in this question
Related
- All Eduqas A-Level Physics revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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