P1 B Revision

P1b physics revision GCSE

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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
The amount of energy transferred depends on the wave length
The wave length is the distance from one wave peak to the next wave peak along the waves
The frequency is the number of complete waves passing past a point per second
Wave speed (metre/second, m/s) = frequency (hertz, Hz) x wavelength (metre, m)
Gamma Rays and xrays
Xrays and gamma radiation are absorbed by dense materials in bone and
by metal.
Xrays and gamma radiation damage living tissue when they pass through
Xrays are used in hospitals to take a radiograph picture. They pass
through soft tissue but they are absorbed by bones and thick metal
Gamma rays are used to kill harmful bacteria in food, to sterilise
surgical equipment and to kill to cancer cells.
Light and ultraviolet radiation
Light from lamps and the sun is called white light because it has all the colours of the spectrum in it
Human eye doesn't detect ultraviolet or infrared
Ultraviolet radiation is electromagnetic radiation between violet light and xrays in wavelength
Ultraviolet light makes some chemicals emit light
Ultraviolet light is harmful to the eye and can cause blindness
Electromagnetic waves directed at substances, the surface of the substance and wavelength can determine
whether the waves are totally, partially or not reflected at all
Light on glass are partially reflected
Xrays directed at plastic are not reflected at all
Some waves are absorbed by the substance ­ would increase the temperature ­ could create alternating
Waves that are not reflected or absorbed are transmitted ­ substance and wavelength depend on whether a
wave is transmitted or not
UV is mostly absorbed by glass
Xrays mostly pass through tissue but is absorbed by bone
Infrared, microwaves and radio waves
All objects emit infrared. The hotter the object, the more infrared it emits
Infrared is absorbed by the skin ­ kills/damages skin cells because it heats up the cells
Infrared Devices
Infrared scanners/cameras
Optical fibres
Remote control handsets
Shorter in wavelength that radio waves

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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 and Lower frequency
Used for
Radio waves emitted from an aerial when an alternating current is passed through it ­ frequency of radio waves
is the same as the frequency of an alternating current
Communication…read more

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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 can be sent using digital signals
Pulses can be made shorter so more pulses can be sent per second
Observing nuclear radiation
Henri Becquerel ­discovered Uranium salts pass out radiation that is able to…read more

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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 contains a tiny amount of the radioactive substance. A detector is placed against
each kidney. For an unblocked kidney ­ the reading goes up then down as it passes through.…read more


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