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How
the
waves fit
into the
spectrum
Radio
waves
Microwaves
Infra-red
Visible
light
Ultra-
violet
X-rays
Gamma
rays
Quick Quiz
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Ultra-Violet
light is made by special lamps,
for example, on sun beds.
It is also given off by the Sun
in large quantities. We call it "UV"
for short.
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Uses for UV
light include getting a sun tan,
detecting forged bank notes
in shops, and hardening some types of dental filling.
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You also see
UV lamps in discos, where they make your clothes glow. This happens
because substances in washing powder "fluoresce" when
UV light strikes them.
When you mark your posessions with a security marker pen, the ink
is invisible unless you shine a UV lamp at it. |
Ultraviolet
rays can be used to kill microbes.
Hospitals use UV lamps to sterilise surgical equipment and the
air in operating theatres. Food and drug companies also use UV
lamps to sterilise their products
Suitable doses
of Ultraviolet rays cause the body to produce vitamin D, and this
is used by doctors to treat vitamin D deficiency and some skin
disorders.
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Large doses
of UV can damage the retina
in your eyes, so it's important to check that your sunglasses will
block UV light.
The cheaper
sunglasses tend not to protect you against UV, and this can be really
dangerous. When you wear sunglasses the pupils of your eye get bigger,
because less light reaches them.
This means that
if your sunglasses don't block UV, you'll actually get more
ultra-violet light on your retinas than if you didn't wear them!
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Large doses
of UV cause sunburn and even
skin cancer. Fortunately,
the ozone layer in the Earth's atmosphere screens us from most
of the UV given off by the Sun. Think of a sun tan as a radiation
burn!
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