Visible Light and Colour
Master Visible Light and Colour for GCSE Physics with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. A separate (triple) physics topic: the colour of an opaque object depends on which wavelengths it reflects and absorbs, and filters transmit only certain colours.
Free downloads
These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Objects appear coloured because of the way they reflect, absorb and transmit different wavelengths of visible light. This is a Triple-only topic.
An opaque object that is not a primary source of light appears the colour of the light it reflects most strongly. A red object reflects red light and absorbs the other wavelengths. A white object reflects all wavelengths equally, and a black object absorbs all of them.
Colour filters work by absorbing certain wavelengths and transmitting others. A red filter transmits red light and absorbs all other colours, which is why a blue object viewed through a red filter appears black — no light reaches the eye.
Revision notes
Why objects appear coloured
An opaque object appears the colour of the light it reflects most strongly.
A red object reflects red light and absorbs the other wavelengths. White objects reflect all wavelengths equally; black objects absorb all wavelengths.
Colour filters
A filter absorbs certain wavelengths and transmits others.
A red filter transmits only red light and absorbs all other colours. Only the transmitted light passes through to the eye.
Combining objects and filters
A blue object viewed through a red filter appears black.
The blue object reflects only blue light, and the red filter absorbs blue, so no light reaches the eye. Working through what is reflected and then what is transmitted answers all such questions.
Key points
- Objects appear the colour they reflect most.
- A red object reflects red and absorbs other colours.
- White reflects all wavelengths equally.
- Black absorbs all wavelengths.
- Filters transmit some wavelengths and absorb others.
- A blue object through a red filter appears black.
Worked examples
Example 1
Explain why a red book appears red in white light. [2 marks]
Model answer
The book reflects red light most strongly (1 mark) and absorbs the other wavelengths of visible light, so only red light reaches the eye (1 mark).
Example 2
Explain what happens when a blue object is viewed through a red filter. [3 marks]
Model answer
The blue object reflects only blue light (1 mark). The red filter absorbs blue light and transmits only red (1 mark). No light therefore reaches the eye, so the object appears black (1 mark).
Example 3
Explain why a white object appears white. [2 marks]
Model answer
It reflects all wavelengths of visible light equally (1 mark), and the combination of all wavelengths is seen as white (1 mark).
Common mistakes
Saying a coloured object produces its own light.
It reflects the light falling on it; only a primary source produces light.
Saying a filter adds colour.
It absorbs some wavelengths and transmits others — it cannot add anything.
Forgetting that black means no light reaches the eye.
An object appears black when all light is absorbed.
Not working through both stages.
Consider what the object reflects, then what the filter transmits.
Exam tips
- Work through reflection first, then transmission.
- Say the object reflects rather than produces light.
- Explain black as all light absorbed.
- Remember this is a Triple-only topic.
Key terms
- Opaque
- Not allowing light to pass through.
- Filter
- A material transmitting some wavelengths and absorbing others.
- Reflect
- To bounce light off a surface.
- Transmit
- To allow light to pass through.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.