Electromagnetic waves and communication
- Created by: jaaaz_v
- Created on: 11-06-15 22:14
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- EM Waves and Communication
- Radio waves
- Wavelengths longer than around 10cm
- Long wavelengths diffract around the curved surface of the earth
- So can be transmitted to all over the world
- Can also diffract around hills and tunnels
- Diffraction makes it possible for the radio signals to the receiver even if they're not in sight of the transmitter
- The waves used for TV's and radio have short wavelength
- To get reception you must direct sight of the transmitter
- signal doesn't bend around hills or go through buildings
- Microwaves
- Used for communication to and from a satellite
- Signal from a transmitter is transmitted into space where its picked up by the satellites receiver dish
- Satellite then transmits the signal back onto earth
- Where its received on a satellite dish
- Satellite then transmits the signal back onto earth
- Some wavelengths of microwaves are absorbed by water molecules and heat them up
- Could damage our cells if we use the phone too much
- Infrared waves
- Used in wireless remote controllers
- Remote controls work by emitting different patterns of infrared waves to send different commands to an appliance
- Optical fibers use both infrared waves and visible light to carry data over long distancs quickly
- Signal is carried as pulses of light or infrared radiation and is reflected off the sides of the fiber
- Visible light
- Used for photography
- Cameras get the lens to focus visible light onto a light sensitive film or sensor
- EM Waves
- Have different wavelengths and so have different properties
- Different types of EM waves travel at the same speed
- Waves with higher frequencies have shorter wavelengths
- Radio waves
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