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P1b revision ­ Radiation and the Universe

Electromagnetic Waves
The electromagnetic spectrum
Electromagnetic waves are electric or magnetic disturbances that transfer energy from one place to
another
The amount of energy transferred depends on the wave length
The wave length is the distance from one wave peak to the next…

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Lies between radio waves and infrared radiation
Used for
Communications ­ can pass through the atmosphere because they don't spread out as much as radio waves
Heating food in microwaves ­ unlike infrared, microwaves penetrate food


Radio Waves
Range from 300 000 Hz to 3000 million Hz
Longer in wavelength…

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Digital radio transmitters, scanners and fax machines convert analogue to digital signals before they are sent
To send an analogue signal
Waves are used to modulate the carrier waves
Amplitude or frequency is modulated in the process
Digital signals suffer less interference so it gives higher quality
Much more information…

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Automatic thickness monitoring:
When making metal foil. A detector is on the other side of the foil. Radiation is passed through it. If the foil is
too thick the reading drops. The detector sends a signal to the rollers which make the foil thinner
Radioactive tracers:
Patient drinks water which…

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