Energy
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Colour. (2026). In Q-files Encyclopedia, Science, Energy. Retrieved from
https://www.q-files.com/science/energy/colour
"Colour." Science, Energy, Q-files Encyclopedia, 10 Mar. 2026.
https://www.q-files.com/science/energy/colour.
Accessed 13 Sep. 2026.
Colour 2026. Science, Energy. Retrieved 13 September 2026, from
https://www.q-files.com/science/energy/colour
Science, Energy, s.v. "Colour," accessed September 13, 2026.
https://www.q-files.com/science/energy/colour
Colour
Sunlight is not colourless, but is made up of all the colours of the rainbow: the spectrum of light. We see these colours when a rainbow forms. In fact, only three, red, green and blue (called primary colours), are needed for our eyes to see every colour there is. Many different colours can be made by mixing together primary colours in different amounts.
Using a prism
The different colours of light can be seen when white light is split up using a prism, an angled block of transparent material such as clear glass or plastic. As the light waves pass into and then out of the prism they are bent or refracted. Longer waves of red light refract least. Shorter waves of violet light refract most. The other colours, orange, yellow, green and blue, are spread out between them.
A raindrop works as a natural prism. Sunlight separates into different colours on entering a raindrop, as red light is refracted by a lesser angle than blue light. The light rays reflect off the back of the raindrop and fan out as they leave the raindrop. The greatest intensity is at an angle of about 42°. Millions of raindrops together form a rainbow.
Spectrum of light
The section of the electromagnetic spectrum that we can see is called the spectrum of light. It is formed of all the different colours that make up white light: red, orange, yellow, green, blue, indigo and violet.
Colours exist because light is in the form of waves and not all the waves have the same wavelength. Some are slightly longer than others, and these we see as red. Light waves of medium wavelength appear to our eyes as green. We see the shortest light waves as violet. A leaf is green because its surface absorbs all the colours in white light except green, which it reflects into our eyes. A red flag absorbs all colours except red. Objects that reflect all colours are white.
Adding colours
We see colours on screens in different ways. A TV or computer screen has thousands of tiny dots that glow and give out light. These dots have actually only three colours—red, green and blue. These colours are known as the primary colours of light. Added to each other in different combinations and brightness they can make any other colour. For example, red and green together make the colour yellow. Red and blue produce the pinky colour known as magenta. Blue and green form cyan, a type of turquoise. The three primary colours of red, blue and green added together make white light.
On the screen of a computer or TV the dots are arranged in groups known as pixels. The different colours of dots flash on and off in different combinations and shine with different brightnesses. From a distance, the eye cannot see the individual dots. They merge to produce larger areas of colour.
Consultant: Mike Goldsmith
pics
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