Green Light Projected onto a Dark Surface




To find out more about the diagram above . . . . read on!

Green Light Projected onto a Dark Surface

Look carefully at the diagram at the top of the page. Now check out the following questions (and answers)!

  1. Name the three colours and their corresponding wavelengths of light that when mixed together in equal proportions make white?
  2. What are RGB primary colours?
  3. What are additive primary colours?
  4. What are secondary colours?
  5. What are the thee CMY primary colours?

About the Diagram

Introducing the diagram! Read back and forward between the image at the top of the page and the explanation below!

This is one of a set of 3 diagrams showing torches projecting red, green and blue light onto a neutral coloured surface.

A fourth diagram shows what happens when all three are on at the same time and their beams partially overlap one another.

Understanding the diagrams:

  • The diagrams illustrate how the RGB colour model works in practice.
  • Each torch emits light at the same intensity.
  • Each torch points towards a different area of the surface.
  • The light in each case is of a single wavelength so produces a spectral colour.
  • The selected wavelengths are: red = 660 nanometres (nm), green = 525 nm, blue = 460 nm.

About the RGB colour model

  • RGB colour is an additive colour model that combines wavelengths of light corresponding with the red, green and blue primary colours to produce other colours.
  • RGB colour is called a model because it is a method that can be followed to produce a full gamut of colours.
  • Red, green and blue are called additive primary colours in an RGB colour model because they can be added together to produce all other colours.
  • Each of the three beams is called a component of the resulting colour.
  • Different colours are produced by varying the intensity of the component colours between fully off and fully on.
  • When any two fully saturated additive primaries are combined they produce a secondary colour: yellow, cyan and magenta.
  • When fully saturated red, green and blue primary colours are combined they produce white.
  • Some RGB colour models can produce over 16 million colours by varying the proportion and intensity of each of the three component primary colours.
  • The additive RGB colour model cannot be used for mixing different colours of pigments, paints, inks, dyes or powder. To understand these colourants find out about subtractive colour.

Follow the blue links for definitions . . . . or check the summaries of key terms below!

Some Key Terms

Move to the next level! Check out the following terms.

Light source

A light source is a natural or man-made object that emits one or more wavelengths of light. The Sun is ...
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Primary colour

Primary colours are a set of colours from which others can be produced by mixing (pigments, dyes etc.) or overlapping ...
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RGB colour

To be clear about RGB colour it is useful to remember first that: The visible spectrum is the range of ...
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Colour model

A colour model is a mathematical system used to describe colours using a set of numeric values. A colour model ...
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Wavelength is a measurement from any point on the path of a wave to the same point on its next ...
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White light

White light is the name given to visible light that contains all wavelengths of the visible spectrum at equal intensities ...
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