G9 Wave Model Electromagnetic Waves

Gapfill exercise

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   diffract      electric      electrical      electrons      energy      fluoresce      highest      hot      increases      interference      ionosphere      less      magnetron      ozone      radio      radioactive      shorter      signals      space      sterilisation      transmitters      UHF      vacuum      very      VHF      violet      water   
Electromagnetic waves share some common properties.

1. They can travel through empty space (a )
2. They all travel at the same speed 3X 10 8m/s through a
3. They are all transverse waves made up of and magnetic waves.
4. They transfer .

The electromagnetic waves are a large family of waves, from gamma rays which have the smallest wavelength up to radio waves with the longets wavelength.

Only some electromagnetic waves can pass through the Earth's atmosphere.
Visible light can pass through, as can UHF and VHF waves.

Infrared waves
Beyond the red end of the spectrum, and out of the range of electromagnetic waves that our eyes can detect are infra-red waves. These are given out by warm objects. As the object gets warmer, the object gives out shorter wavelength infreared waves.
Most solids absorb infrared, causing them to heat up.
Short-wavelength infrared can pass through clear glass and plastics, which is how a greenhouse warms up. Inside the greenhouse, longer wavelength infrared is reflected back up but this cannot pass through the glass, so the heat is traped inside the greenhouse.
Infrared is used in security lamps, in night-vision goggles and in remote controls for TVs.

Ultraviolet waves
Very objects emit waves beyond the end of the visible spectrum. This is ultraviolet radiation.
Some materials when they absorb UV.
Most of the Sun's UV is absorbed by the in the Earth's atmosphere.

Ionising radiations
Ultraviolet and wavelengths with wavelengths are all known as ionising radiations. They can remove the from atoms which can damage or destroy cells.

X-rays have shorter wavelengths than UV. They are given off when fast-moving electrons lose very quickly.
Short-wavelength X-rays are penetrating. Long-wavelength X-rays are penetrating and are used to X-ray broken bones. X-rays can be dangerous, so exposure times are kept to a minimum.

Gamma Rays
Gamma rays come from some materials.They can be used in the treatment of cancer and for X-ray type photographs.They are also used to kill cells and bacteria in of medical equipment.

Radio and Microwaves
Diffraction is important for radio waves - long and medium waves around hills and other obstacles. Medium waves are also reflected from the which their range.
Radio waves can be made by making an current flow back and forth quickly in an aeriel. To carry information, the radio waves are varied to create .
is used for stereo radio and for TV broadcasts. VHF and UHF do not diffract so much, so you need a direct line from the transmitter to the receiver.
Microwaves have the frequencies of all the radio waves and are used by mobile phones and satellite TV. Satellites are used for them because the microwaves are not reflected or absorbed by the ionosphere. Microwaves do not around objects so many towers are needed. Radar also uses microwaves. Pulses of microwaves are sent out from the ship and some get reflected back off the object.
Radio Interference
This happens when you travel along a road between two and the two sets of radio waves interfere. Radio waves can also be reflected back from aircraft, so people living under flight paths can suffer radio when aircraft fly over.
Listening for Aliens
Radio telescopes are used to detect UHF and VHF waves that travel through . We hope that aliens might send out radio signals which we will then be able to detect.
Microwave ovens
Like all electromagnetic waves, microwaves make objects warm up. Water it very good at absorbing microwaves. Microwaves penetrate deep into the food and make the in it heat up. The part of a microwave oven that emits the radiation is called a .