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 is shone onto objects or through materials, different colours can be seen.
Model answer (5 marks)
1. The colour we see from an object is the frequency of light that is reflected by it.
2. The object absorbs all other frequencies of the incident white light.
3. A white object reflects essentially all frequencies, while a black object absorbs almost all.
4. A colour filter transmits only one frequency (colour) of light.
5. The filter absorbs all other frequencies of the white light.
2. The object absorbs all other frequencies of the incident white light.
3. A white object reflects essentially all frequencies, while a black object absorbs almost all.
4. A colour filter transmits only one frequency (colour) of light.
5. The filter absorbs all other frequencies of the white light.
Examiner tips
- Use the word ‘frequency’ or ‘wavelength’ to show understanding of light properties.
- Show the absorption/reflection process for the object and the filter separately.
- Mention that the reflected/ transmitted light is what we perceive as colour.
- Keep the answer concise and directly linked to the marks scheme points.
Common mistakes
- Confusing reflected light with transmitted light for objects.
- Saying the object ‘emits’ the colour instead of ‘reflects’ it.
- Using ‘colour’ instead of ‘frequency’ or ‘wavelength’ in the explanation.
Mark scheme (5 marks)
- The colour of an object is determined by the frequency of light that is reflected from it
- An object absorbs all other colours (frequencies) of light except the one it reflects
- A white object reflects all colours / a black object absorbs all colours
- A colour filter only allows light of a single colour (single frequency) to pass through it
- The colour filter absorbs all other colours (frequencies) of the white light
Key terms in this question
Related
- All WJEC A-Level Physics (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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