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They all travel at the speed of light
They can all travel through a vacuum
The differences in the waves are due to their :
Penetrative powers
The electromagnetic spectrum…read more

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Cooking with microwaves
A microwave oven uses radio waves to cook food very
The microwaves are produced by a ` magnetron ' and
guided by a metal stirrer which reflects the waves into
different parts of the oven
Microwaves are reflected by metal but absorbed by food
( about 1 cm )
The waves have a wavelength of 12 cm at a frequency of
2500 MHz
At this frequency the electromagnetic waves are absorbed
by water molecules in the food, heating them up and…read more

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The door must have a safety switch to turn of the
microwaves if you open the door ­ otherwise you could burn
your fingers!
Microwaves are also used for communicating with satellites
The water molecules in the outer layers vibrate more and
their kinetic energy increases
The energy is transferred to the rest of the food by
conduction and convection…read more

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Infra ­ Red cookery
Energy from infra ­ red is absorbed by particles on the
surface of the food
This increases the kinetic energy of the particles
The energy is transferred to the rest of the food by
The differences between Infra ­ Red cooking and
microwave cooking…read more

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Although microwaves are lower energy than infra ­ red and can
pass through glass and plastic, they can still cause burns, when
absorbed by body tissue
Frequency = 2450 MHz
Distance = 10 cm
Speed = 2.45 X 109
Microwaves in communications
Slightly lower energy waves are used in communications
e.g.…read more

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The transmitters have to be fairly close together
otherwise diffraction ( spreading out of the wave ) and
( where signals cross over / meet ) can cause loss of signal
Dangers of microwaves in communications
Microwaves are used for communication as well as cooking
Recently there have been reports about dangers of mobile
Newspaper headlines have read " microwaves don't fry the
brain, they just warm it "
There is no scientific proof one way or another
There is some evidence of…read more

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