Addition and Subtraction of Light

8.7 Addition and
Subtraction of Light

• Identify primary colours
• colours to proIdentify the addition of primary duce secondary colours

• Communicate about subtraction of light
• Explain addition and subtraction of light

m/s 241-246

Coloured lights can be categorised into two types,namely primary

colour and secondary colour. The primary colour is the basic colour
that cannot be produced throught colour mixing. Red,blue and green

are primary colour.

Thi s Photo by Unknown Author i s licensed under CC BY-SA-NC

What is the colour
produced when two
primary colours are
mixed?

Colours produced from Thi s Photo by Unknown Author i s licensed under CC BY-SA
the mixing of two colours
are known as secondary
colours.White colour is
produced when all the
three primary colours are
mixed together.

The Subtraction of Light

// Thelightwhichhasthesamecoloursas thecolourof theopaqueobjectswillbe
reflecteddirectlyintooureyes,whilethelightof othercolourswillbeabsorbedbythe
objects.

Thi s Photo by Unknown Author i s licensed under CC BY-SA

Thi s Photo by Unknown Author i s licensed under CC BY-NC

The Principle of *Objects with primary colours[red,blue
Light
or green]will only reflect the light which
Subtraction has the same colours as them.

*Objects with secondary colours

[yellow,magenta or cyan]reflect the light
of the same colour and also the light of

primary colours which form the
secondary colour.

*White objects appear white in light

because the white objects reflect all
colours in white light.

*Black objects appear black because

they absorb all colours in white light.

Usually,colour filters are used to understand the principle
of subtraction.

Primary colour filters Secondary colour filters

• Allow only the light of the same • The light of primary colours which
colour to pass through,light of from the secondary colour to pass
other colours are absorbed. through.Light of other colours are
absorbed.

Thi s Photo by Unknown Author i s licensed under CC BY-SA-NC

Thi s Photo by Unknown Author i s licensed under CC BY-SA

Example of Addition
and Subtraction of
Light

Thi s Photo by Unknown Author i s licensed under CC BY-SA

Thi s Photo by Unknown Author i s licensed under CC BY-SA-NC Thi s Photo by Unknown Author i s licensed under CC BY-SA

Thi s Photo by Unknown Author i s licensed under CC BY-SA