You Shine a Red Light on a Blue Object

Contents

• 1 Key Stage 1
  • 1.1 Meaning
  • 1.2 About Colours
  • 1.3 Examples
• 2 Key Stage 3
  • 2.1 Meaning
  • 2.2 About Colour
  • 2.3 Colour and Objects
  • 2.4 Eyes and Colour
  • 2.5 Coloured Mixing
    • 2.5.1 Primary Colours
    • 2.5.2 Secondary Colours
  • 2.6 Colour Filters
• 3 Key Stage 4
  • 3.1 Meaning
  • 3.2 About Colour
  • 3.3 Eyes and Colour
  • 3.4 Coloured Mixing
    • 3.4.1 Additive Colours
  • 3.5 Colour and Reflection
    • 3.5.1 Subtractive Primary Colours
    • 3.5.2 Coloured Objects Under Light Coloured Light
  • 3.6 Colour Filters
  • 3.7 References
    • 3.7.1 AQA
    • 3.7.2 Edexcel
    • 3.7.3 OCR

Key Stage 1

All the colours in the rainbow.

Meaning

Colour is something we see with our eyes.

Singular Noun: Colour

Plural Noun: Colours

Verb: Colour

About Colours

The colours we can see are red, orange, yellow, green, blue, indigo and violet. If you mix colours of paint together you can get another colour. Red and yellow paint mixed together makes orange. Blue and yellow paint mixed together make green. Blue and red paint mixed together makes purple. If you mix all three you can make brown.

Examples

Grass is a green colour.	The colour of this rose is red.
The sky is blue in colour.	I will colour in The Sun yellow with paint.

Key Stage 3

Meaning

Colour is a property of objects that we can see.

About Colour

White light can be divided into 7 colours:

• Red
• Orange
• Yellow
• Green
• Blue
• Indigo
• Violet

Red light has the lowest frequency and the longest wavelength.

Violet light has the highest frequency and the shortest wavelength.

Colour and Objects

Eyes and Colour

The human eyes only have three different colour sensing cells called cones. They can detect; red, green or blue light. All other colours we see are caused by a pair of different cones detecting light at the same time.

If the red cones and blue cones both detect light then we see magenta.

If the red cones and green cones both detect light then we see yellow.

If the blue cones and green cones both detect light then we see cyan.

Coloured Mixing

Magenta can be made by mixing red and blue light. Yellow can be made by mixing red and green light. Cyan can be made by mixing blue and green light. White can be made by mixing red, blue and green light.

Primary Colours

Primary Coloured Objects

A red object appears red under red light. A blue object appears black under red light. A green object appears black under red light.

A red object appears black under blue light. A blue object appears blue under blue light. A green object appears black under blue light.

A red object appears black under green light. A blue object appears black under green light. A green object appears green under green light.

Secondary Colours

Secondary Coloured Objects

A yellow object appears red under red light. A cyan object appears black under red light. A magenta object appears red under red light.

A yellow object appears black under blue light. A cyan object appears blue under blue light. A magenta object appears blue under blue light.

A yellow object appears green under green light. A cyan object appears green under green light. A magenta object appears black under green light.

Secondary Coloured Lights

A red object appears red under yellow light. A blue object appears black under yellow light. A green object appears green under yellow light.

A red object appears black under cyan light. A blue object appears blue under cyan light. A green object appears green under cyan light.

A red object appears red under magenta light. A blue object appears blue under magenta light. A green object appears black under magenta light.

Colour Filters

Primary Coloured Filters

Through a red filter: A red object appears red. A blue object appears black. A green object appears black. A yellow object appears red. A cyan object appears black. A magenta object appears red.

Through a blue filter: A red object appears black. A blue object appears blue. A green object appears black. A yellow object appears black. A cyan object appears blue. A magenta object appears blue.

Through a green filter: A red object appears black. A blue object appears black. A green object appears green. A yellow object appears green. A cyan object appears green. A magenta object appears black.

Primary Coloured Filters

Through a yellow filter: A red object appears red. A blue object appears black. A green object appears green. A yellow object appears yellow. A cyan object appears green. A magenta object appears red.

Through a cyan filter: A red object appears black. A blue object appears blue. A green object appears green. A yellow object appears green. A cyan object appears cyan. A magenta object appears blue.

Through a magenta filter: A red object appears red. A blue object appears blue. A green object appears black. A yellow object appears red. A cyan object appears blue. A magenta object appears magenta.

Key Stage 4

Meaning

Colour is a property of objects that we can see.

About Colour

White light can be divided into 7 colours:

• Red
• Orange
• Yellow
• Green
• Blue
• Indigo
• Violet

Red light has the lowest frequency and the longest wavelength.

Violet light has the highest frequency and the shortest wavelength.

An object may appear to have a colour for three reasons:

• Reflection - An object may reflect some frequencies while absorbing others.
• Filtering - An object may be viewed through a transparent medium which absorbs certain frequencies of light.
• Scattering - An object may be viewed through a transparent medium which scatters certain frequencies of light. This is why the sky appears blue and the Sun appears yellow.

Eyes and Colour

The human eyes only have three different colour sensing cells called cones. They can detect; red, green or blue light. All other colours we see are caused by a pair of different cones detecting light at the same time.

If the red cones and blue cones both detect light then we see magenta.

If the red cones and green cones both detect light then we see yellow.

If the blue cones and green cones both detect light then we see cyan.

Coloured Mixing

Additive Colours

The additive primary colours are Red, Blue and Green. This means when two colours of light are added, they make new colours.

Magenta can be made by mixing red and blue light. Yellow can be made by mixing red and green light. Cyan can be made by mixing blue and green light. White can be made by mixing red, blue and green light.

Colour and Reflection

Subtractive Primary Colours

Mixing Magenta and Cyan paints makes a new paint which absorbs green light and red light. The new paint appears blue because that is the only colour it reflects.

Mixing Cyan and Yellow paints makes a new paint which absorbs red light and blue light. The new paint appears green because that is the only colour it reflects.

Mixing Magenta and Yellow paints makes a new paint which absorbs green light and blue light. The new paint appears red because that is the only colour it reflects.

Adding a little extra of one colour over another can go on to give different colours.

Magenta > Cyan gives purple.

Cyan > Magenta gives pale blue.

Cyan > Yellow gives turquoise.

Yellow > Cyan gives lime green.

Magenta > Yellow gives pink.

Yellow > Magenta gives orange.

Colour exists because objects absorb some frequencies of light but reflects other frequencies.

A coloured object absorbs some colours and reflects others appearing the colour of the reflected light. For example leaves are green because the chlorophyll inside them absorbs red and blue light but not green.

When coloured objects are mixed such as paint they absorb certain colours. The more different colour paints added, the more colours they absorb.

In art the focus is on these subtractive primary colours; Magenta, Cyan and Yellow. When objects with these colours are mixed the object will preferentially absorb certain frequencies of light allowing only certain colours to be reflected.

Coloured Objects Under Light Coloured Light

Light Colour	Object Colour	Appearance
Red	Red	Red
	Blue	Black
	Green	Black
	Magenta	Red
	Cyan	Black
	Yellow	Red
Blue	Red	Black
	Blue	Blue
	Green	Black
	Magenta	Blue
	Cyan	Blue
	Yellow	Black
Green	Red	Black
	Blue	Black
	Green	Green
	Magenta	Black
	Cyan	Green
	Yellow	Green
Magenta	Red	Red
	Blue	Blue
	Green	Black
	Magenta	Magenta
	Cyan	Blue
	Yellow	Red
Cyan	Red	Black
	Blue	Blue
	Green	Green
	Magenta	Blue
	Cyan	Cyan
	Yellow	Green
Yellow	Red	Red
	Blue	Black
	Green	Green
	Magenta	Red
	Cyan	Green
	Yellow	Yellow

Colour Filters

Colour filters work by absorbing some frequencies of light while transmitting others.

Looking through a colour filter makes any object whose colour is absorbed appear black.

Colour Filter	Object Colour	Appearance
Red	Red	Red
	Blue	Black
	Green	Black
	Magenta	Red
	Cyan	Black
	Yellow	Red
Blue	Red	Black
	Blue	Blue
	Green	Black
	Magenta	Blue
	Cyan	Blue
	Yellow	Black
Green	Red	Black
	Blue	Black
	Green	Green
	Magenta	Black
	Cyan	Green
	Yellow	Green
Magenta	Red	Red
	Blue	Blue
	Green	Black
	Magenta	Magenta
	Cyan	Blue
	Yellow	Red
Cyan	Red	Black
	Blue	Blue
	Green	Green
	Magenta	Blue
	Cyan	Cyan
	Yellow	Green
Yellow	Red	Red
	Blue	Black
	Green	Green
	Magenta	Red
	Cyan	Green
	Yellow	Yellow

References

AQA

Colour, page 226-7, GCSE Physics; Student Book, Collins, AQA

Colour, pages 206-207, GCSE Physics; Third Edition, Oxford University Press, AQA

Colour, pages 253, 254, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA

Colours, page 85, GCSE Physics; The Revision Guide, CGP, AQA

Filters (colour), page 254, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA

Filters (colour), page 85, GCSE Physics; The Revision Guide, CGP, AQA

Edexcel

Colour, pages 68-69, GCSE Physics, Pearson Edexcel

OCR

Colour, pages 164-165, Gateway GCSE Physics, Oxford, OCR

Colours; bromine reactions, page 233, Gateway GCSE Chemistry, Oxford, OCR

Colours; equilibrium position, page 189, Gateway GCSE Chemistry, Oxford, OCR

Colours; manganite/manganese ions, page 327, Gateway GCSE Chemistry, Oxford, OCR

Colours; metal hydroxide precipitates, page 149, Gateway GCSE Chemistry, Oxford, OCR

Colours; silver halide precipitates, page 151, Gateway GCSE Chemistry, Oxford, OCR

Colours; transition metal compounds, page 141, Gateway GCSE Chemistry, Oxford, OCR

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Source: https://www.keystagewiki.com/index.php/Colour

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