P4 Physics pg 95
- Created by: Abigail Swann
- Created on: 04-04-13 12:57
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- Radio waves and Microwaves
- EM waves have different frequencies and act differently in the atmosphere
- Below 30 MHz - radio waves are reflected of the ionosphere (waves travel longer)
- Between 30 MHz and 30 GHz - radio/microwaves pass through atmosphere (transmissions must be in line of sight)
- Above 30 GHz - microwaves are scattered and absorbed by rain/dust (reduces strength of signal)
- Dishes are used to receive microwaves signals
- Normal tv/radio signals transmit using radiowaves which are recieved by an aerial
- Use a dish as the wavelength of microwaves are too short for aerials
- The dishes are a lot larger than the wavelenth, this reduces refraction and produces a narrow beam
- Long wavelength radio waves diffract
- Long wavelength radio waves have a large range (good for broadcasting)
- Waves diffract when they pass through a narrow gap or past an object
- The longer the wavelength of a wave, the more it will diffract (narrow gap = size of wavelength)
- EM waves have different frequencies and act differently in the atmosphere
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