iSCIENCE
SEEING COLOURS
SPECTRUM
Usually, all the colours you can imagine join up and
travel together to make what is called white light.
When white light from the sun shines through your
lunchtime glass of water, for example, you might find
a rainbow of colours displaying on the table top.
The word 'Spectrum' was first used to mean the
range of colours visible in a rainbow or through a
prism. As Scientists continued investigating light,
they realised it travels in a wave form and each
different colour has its own wavelength. They also
discovered 'new' wavelengths of coloured light that
had been hidden from us because generally they
can't be seen by human eyes, although some can be
detected by birds, insects and fish.
-Try it!
A 'prism' is a special shape of glass with lots of flat
sides that works particularly well at taking white light
and separating out the blended colours.
-Try this, too, if you have a prism!
Other places you might notice this happening are in
a single raindrop – or even where sunlight hits water
droplets in the right conditions and makes a beautiful
single ('primary') rainbow.
In a primary rainbow, Red is on the 'top' (the longest,
outer side) and the colours are always in the
sequence: Red – Orange – Yellow – Green – Blue –
Indigo – Violet.
Double rainbows happen sometimes! Look closely
and you will see the 'secondary' rainbow always has
its colours in the opposite order, with Red on the
'bottom', shorter side.
This 'invisible' long-wavelength light is called Infrared
(IR) and is used in things like remote controls.
Microwaves and radio waves are also at this end of
the spectrum. The short-wavelength light is called
Ultraviolet (UV) light and the spectrum continues into
X-rays and gamma rays.
RIDDLE
Q:
A:
I have a rainbo
w in front of m
e–
where is the su
n?
“It's behind you!
CHECK OUT:
•
•
•
•
•
iMATHS
iTECH
iWORDS
ACTIVITY : THINKING SKILLS & SCIENCE
COOL WEBLINKS
!”
- But seriously...
it really will be
behind you! Prov
e it to yourself
next time you se
e a rainbow.
FUSE
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