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The visible spectrum
I can describe what white light is, and explain why a visible spectrum can be produced from white light.
Lesson 2 of 7
New
New
- Year 8
The visible spectrum
I can describe what white light is, and explain why a visible spectrum can be produced from white light.
Lesson details
Key learning points
- White light from the Sun and light bulbs consists of light of all the colours in the visible light spectrum (a rainbow).
- A transparent triangular prism can split up sunlight into a visible light spectrum.
- The visible light spectrum shows the range of colours that light can have.
- Cone cells in the eye detect colour. There are 3 kinds (R, G and B); each is sensitive to a range of colours of light.
- The colour we see depends on which cone cells are triggered to send a signal to the brain.
Keywords
White light - Light that consists of red, green and blue light in equal amounts so looks white.
Triangular prism - A uniform 3D shape with triangular ends.
Visible light spectrum - A rainbow pattern of coloured light that always occurs with the colours in the same order.
Cone cells - The cells at the back of the eye that detect colour.
Common misconception
Sunlight is yellow(ish), not white.
Show pupils a yellow light (and illuminate white paper beneath a yellow light) and compare it to sunlight to show that sunlight is white.
Our eyes detect all colours of light (not just R, G and B). Each kind of cone cell detects a different range of wavelengths, and the three ranges overlap (e.g. yellow light of a single wavelength triggers both the 'R' and 'G' cones). The concept of wavelength of light is best left until later units.
Teacher tip
Equipment
Ray lamps, slits, transparent triangular prisms, red filters (to fit in the ray lamps).
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
This content is © Oak National Academy Limited (2026), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.A person has an object that they can see through clearly. The object transmits light so it can be described as being...
A person has an object that they can see through clearly. The object transmits light so it can be described as being...
translucent.
opaque.
invisible.
Q2.The back surface of the eye that detects light is called the .
The back surface of the eye that detects light is called the .
Q3.How many types of cone cell are in the eye of a person who has full colour vision?
How many types of cone cell are in the eye of a person who has full colour vision?
0
1
2
Q4.Which of the following explains why we see mainly in shades of grey in dim light?
Which of the following explains why we see mainly in shades of grey in dim light?
The pupil becomes larger in dim light.
The rod cells do not work well in dim light.
The cone cells all become equally sensitive in dim light.
Q5.Match each set of colours of light with the colour that is seen when they enter a person's eyes. (All of the colours in each set have equal brightness.)
Match each set of colours of light with the colour that is seen when they enter a person's eyes. (All of the colours in each set have equal brightness.)
Q6.The screen on a mobile phone shows a yellow banana. Which of the following explains how it does this?
The screen on a mobile phone shows a yellow banana. Which of the following explains how it does this?
The screen contains yellow coloured dye.
The screen has tiny yellow lights, and these lights are switched on.
The screen splits white light into a rainbow of colours and shows the yellow.
Assessment exit quiz
6 Questions
Q1.A rainbow shows the colours that white light can be separated into. They are always in the same order. This is called the visible light...
A rainbow shows the colours that white light can be separated into. They are always in the same order. This is called the visible light...
band.
plectrum.
range.
scale.
Q2.The diagram shows a 3D shape called a __________. When this shape is made out of glass or clear plastic, it can split white light into its component colours.
The diagram shows a 3D shape called a __________. When this shape is made out of glass or clear plastic, it can split white light into its component colours.
polygon
pyramid
triangle
tetrahedron
Q3.Although a rainbow is actually a continuous range of colours, it is traditionally described as having seven colours. Starting with red, sort the seven colours of a rainbow into the correct order.
Although a rainbow is actually a continuous range of colours, it is traditionally described as having seven colours. Starting with red, sort the seven colours of a rainbow into the correct order.
Q4.Which of the following statements describes how a rainbow is made?
Which of the following statements describes how a rainbow is made?
Each raindrop makes all of the colours of light.
Different raindrops make different colours of light.
Raindrops absorb some colours of white light but not the colours of the rainbow.
Q5.Which of the following can look like white light when it enters our eyes at the same time?
Which of the following can look like white light when it enters our eyes at the same time?
a combination of equal brightness of red and green light
a combination of equal brightness of red, yellow and blue light
Q6.A person looks at a television screen and sees cyan, a secondary colour of light. Which of the following statements are correct?
A person looks at a television screen and sees cyan, a secondary colour of light. Which of the following statements are correct?
The colour cyan does not appear in a rainbow.
Light from the screen is detected by the R cone cells of the person’s eyes.
