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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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Microwaves
are basically extremely high frequency radio waves, and are made
by various types of transmitter.
In a mobile phone, they're made by a transmitter chip and an antenna,
in a microwave oven they're made by a "magnetron". Their
wavelength is usually a couple of centimetres. Stars also give off
microwaves. |
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Microwaves cause
water and fat molecules to vibrate, which makes the substances hot.
Thus we can use microwaves to cook
many types of food.
Mobile
phones use micr
owaves, as they
can be generated by a small antenna, which means that the phone
doesn't need to be very big. The drawback is that, being small,
they can't put out much power, and they also need a line of sight
to the transmitter. This means that mobile phone companies need
to have many transmitter towers if they're going to attract customers. |
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Microwaves are
also used by traffic speed cameras,
and for radar, which is used
by aircraft, ships and weather forcasters.
The most common
type of radar works by sending out bursts of microwaves, detecting
the "echoes" coming back from the objects they hit, and
using the time it takes for the echoes to come back to work out
how far away the object is. |
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Prolonged exposure
to microwaves is known to cause "cataracts"
in your eyes, which is a clouding of the lens, preventing you from
seeing clearly (if at all!) So don't make a habit of pressing your
face against the microwave oven door to see if your food's ready!
Recent research
indicates that microwaves from mobile phones can affect
parts of your brain - after all, you're holding the transmitter
right by your head. The current advice is to keep calls short.
People who work
on aircraft carrier decks wear special suits which reflect microwaves,
to avoid being "cooked" by the powerful radar units in
modern military planes. |
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