Radio waves are EM radiation with wavelengths longer than 10cm
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Why can long-wave radio be received halfway around the world?
Long wavelengths (wavelengths of 1-10km) diffract around the curved surface of the Earth. They can also diffract around hill, into tunnels, etc.
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For TV and FM radio, why do you have to be in direct sight of the transmitter?
The radio waves used for TV and FM radio transmitters have very short wavelengths (10cm-10m), so the signal doesn't bend around hills or travel far through buildings
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Why can short-wave (and medium wave) radio signals be received at long distances from the transmitter?
This is because short-wave radio signals (wavelengths of about 10m-100m) are reflected from the ionosphere - this is an electrically charged layer in the Earth's upper atmosphere.
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Which type of wave is used to communicate to and from satellites?
Microwaves
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Why can't you use radio waves to communicate to and from satellites?
This is because you need to use microwaves which can pass easily through the Earth's watery atmosphere
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How does satellite TV work?
The signal from a transmitter is transmitted into space where it's picked up by the satellite's receiver dish. The satellite then transmits the signal back to Earth in a different direction where it's received by a satellite dish on the ground
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What are two other uses for microwaves?
Mobile phone calls can travel as microwaves between the phone and the nearest transmitter. Some wavelengths of microwaves are absorbed by water molecules and heat them up (used in a microwave)
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Why do some people think that using your mobile a lot is bad for your health?
If the water molecules in your cells heat up, you might start to cook! Some people think that this will also happen is you live near a mast, but there isn't any conclusive evidence either way yet
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How are microwaves used by remote-sensing satellites?
They are used to 'see through' the clouds and monitor oil spill, track the movement of icebergs, see the amount of deforestation, etc.
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Other cards in this set
Card 2
Front
Why can long-wave radio be received halfway around the world?
Back
Long wavelengths (wavelengths of 1-10km) diffract around the curved surface of the Earth. They can also diffract around hill, into tunnels, etc.
Card 3
Front
For TV and FM radio, why do you have to be in direct sight of the transmitter?
Back
Card 4
Front
Why can short-wave (and medium wave) radio signals be received at long distances from the transmitter?
Back
Card 5
Front
Which type of wave is used to communicate to and from satellites?
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