The Principle of Light Subtraction

The Principle of Light Subtraction

The colour of opaque objects depends on the colour of the light reflected into our eyes.

• Objects with primary colours ( red, blue or green ) will only reflect the light which has the same colour as them.

A red object only reflects red light.

Other coloured lights will be absorbed.

Therefore, the object appears red.

• Objects with secondary colours ( yellow, magenta or cyan ) reflect the light of the same colour and also the light of primary colours which from the secondary colour.

• White objects appear white in white light because the white objects reflect all colours in white light.

White objects reflect all colours in white light.

All coloured lights overlap to produce white colour again.

• Black objects appear black because they absorb all colours in white light.

Black objects absorb all colours in white light.

No coloured lights are reflected.

Therefore, the objects appear black.