AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
The colour of an opaque object is determined by which wavelengths of light…
Full specification wording
Visible light (physics only): The colour of an opaque object is determined by which wavelengths of light are more strongly reflected.
Opaque means no light passes through, so everything you see from the object has bounced off its surface.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 4 of 9
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Opaque means no light passes through, so everything you see from the object has bounced off its surface. The surface reflects some wavelengths much more strongly than others, and the mixture that is reflected into your eye is the colour you perceive. A tomato looks red in white light because the long wavelength part of the spectrum is strongly reflected while the rest is absorbed. Because the colour depends on the reflected light, it depends on the light shining on the object as well as on the surface itself: put that tomato under pure green light and it looks black, because there is no red in the incident light for it to reflect.
What earns the marks
- Stating that an opaque object reflects the wavelengths of the colour it appears.
- Stating that the remaining wavelengths are absorbed by the surface.
- Stating that the colour seen depends on the light shining on the object as well as the surface.
- Applying this to coloured illumination, for example a red object appearing black in green light.
Common mistakes and how to put them right
Saying the object gives out or emits its colour rather than reflecting it.
Saying the other wavelengths are transmitted through an object that is opaque.
Assuming a red object looks red under every colour of light.
Answering only with what is reflected and never mentioning what is absorbed.
Exam tips
- Write both halves every time: which wavelengths are reflected and which are absorbed.
- State what light is falling on the object before you state what colour it appears.
- If no matching wavelength is present in the incident light, the answer is 'appears black'.
Try the lesson
The start of the Visible light (physics only): The colour of an opaque object is determined by which wavelengths of light are more strongly reflected. lesson, made from checked teaching notes for this specification point.
Have a go first
An opaque object appears red in white light. Which wavelengths of light does the object reflect most strongly?
Listen
Opaque means no light passes through, so everything you see from the object has bounced off its surface. The surface reflects some wavelengths much more strongly than others, and the mixture that is reflected into your eye is the colour you perceive. A tomato looks red in white light because the long wavelength part of the spectrum is strongly reflected while the rest is absorbed. Because the colour depends on the reflected light, it depends on the light shining on the object as well as on the surface itself: put that tomato under pure green light and it looks black, because there is no red in the incident light for it to reflect. A strong answer earns marks for these points. stating that an opaque object reflects the wavelengths of the colour it appears. stating that the remaining wavelengths are absorbed by the surface. stating that the colour seen depends on the light shining on the object as well as the surface. applying this to coloured illumination, for example a red object appearing black in green light. Exam tip: Write both halves every time: which wavelengths are reflected and which are absorbed.
See it
Key words
Say what each word means before you turn the card.
opaque objects
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selective reflection
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absorption
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See every definition
- opaque objects
- Objects through which no light passes, so everything seen from them has bounced off their surface.
- selective reflection
- The surface reflects some wavelengths much more strongly than others, and the mixture reflected into the eye is the colour perceived.
- absorption
- The remaining wavelengths are taken in by the surface rather than reflected.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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