Electromagnetic Waves - What are Infra-red Waves?
Infra-red Waves are part of the electromagnetic
Sir William Herschel discovered Infra-red waves in 1800.
This was the first discovery of any electromagnetic
waves that were outside the range of the visible spectrum.
are sometimes also called
infra-red radiation or thermal radiation.
How are Infra-red Waves Used for Cooking?
are easily absorbed by materials.
The energy of the wave causes the material to get hot.
We usually think of infra-red radiation as heat.
Ordinary ovens, grills and toasters use infra-red radiation
to cook food (ovens may also cook by convection).
radiation will damage or
(such as skin cells) by burning them.
How are Infra-red Waves Used for Communication?
waves can transmit information through the air
to operate TV's and PVR's by remote control.
Information can also be sent through optical fibres.
What is Thermal Imaging?
waves are used for thermal
In a thermal imaging device, a detector receives
infra-red waves and produces an image where
different colours show the intensity of the waves in
different places. This gives you a 'heat picture'
where hotter objects are orange / red
and colder objects are blue / green.
Thermal imaging is used by
fire fighters to see where the hottest part of the fire is.
What is a PIR?
A device called a PIR (passive
infra-red) is used for security.
When a warm object such as a human or animal
approaches a house, the PIR can detect it against the
colder background and send a signal to switch on an outside light.
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