White objects absorb none of the colours in white light. Black objects absorb all of the colours and reflect no light.
V I B GYOR V I B GYOR ROYG
Fig. 19.3.5 White objects reflect all the colours of white light. Black objects absorb all of them and reflect none
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19.3
We can see colours thanks to nerve cells in our eyes called cones. These are on the retina.
There are three types of cone – each one detects one of the primary colours. A person who lacks or has a faulty cone will be colour blind.
Cells called rods are also found in our eyes. Rods allow us to see in black and white.
Filters
Understanding how objects absorb and emit light can be used to create different colours of light.
A filter can be placed in front of white light to absorb all colours except its own. For example, a blue filter will allow blue light to pass through it and absorb all other colours.
Blue filter
R O Y G B I
V Fig. 19.3.7 A filter absorbs all colours except its own A career in light
Optics is the branch of physics that considers the properties of light. Between the years 2000 and 2012, a Nobel Prize was awarded almost every year for work in optics-related areas. Research the career of one optical scientist and draft an evidence-based report on the contributions this person has made to the study of optics.
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Fig. 19.3.6 A false-coloured scanning electron micrograph of the rods and cones in an eye
Red filter Filters
No light seen
Blue light seen
With your lab partner, discuss what light filters you would use to produce the following colours of light: green, cyan, red, magenta.
