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The continuous electromagnetic spectrum below shows seven wave
groups in order of
decreasing wavelength, increasing frequency and increasing
energy.
The higher the frequency, the more energy the wave has.
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Properties
of microwaves |
Properties
of infrared waves |
They are reflected by metals |
They are reflected by shiny surfaces |
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They penetrate into food by about 1 cm |
They heat the surface of the food |
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They can cause burns when
absorbed by body tissue |
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They go through glass and plastic |
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Higher tier only:
In food, the water particles in the outer layers absorb
microwaves
and heat up. Their
kinetic energy increases and the energy is transferred to the
inner layers of food by
conduction and convection.
In food, the
water particles on the surface absorb infrared. Their kinetic
energy increases
and the energy is transferred to the inner layers of food by
conduction.
Uses of
microwaves
Mobile phones use microwave signals.
Uses of
Infrared
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Remote controls.
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Infrared sensors are used to detect body heat. |
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Security lights and burglar alarms.
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- A
thermogram
is used to identify areas of different
temperatures. See picture bellow.
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