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A yellow object
absorbs all the
wavelengths except
yellow, which it reflects
back to our eyes. The
band of visible colours
that make up light is known
as the spectrum. Each shade
blends into the next, but we
usually divide the spectrum
into seven colours: red,
orange, yellow, green,
blue, indigo, and violet.COLOUR BLINDNESS
Our ability to detect colours depends on
cells on the eye’s retina, which are sensitive
to specific wavelengths of light. The
cells that detect certain parts
of the spectrum are missing or
inactive in a colour-blind person.INTENSITY
On a sunny day, things appear colourful
because our eyes can see differences
in the wavelengths of light. On a dark
day, less light enters the eyes, so we
cannot distinguish wavelengths as
easily and colours look dull.SPLITTING WHITE LIGHT
When white light passes through
a block of glass called a prism,
different wavelengths refract
(bend) different amounts, so
the light splits showing the
colours of the spectrum. When
light passes through raindrops
this effect creates a rainbow.Green plants contain
a green pigment
called chlorophyll114_115_Colour.indd 115 03/01/19 12:10 PM