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P4.Waves (Ian) (EM Spectrum (Ultra-violet (Causes fluorescence in some…
P4.Waves (Ian)
EM Spectrum
Ultra-violet
Causes fluorescence in some materials. Used with sun beds to produce a sun tan and in identifying security marked valuables
X-radiation
Blackens photographic film. Used to take images of bones in medical diagnosis. Dangerous in high doses since ionising
Visible
Produced by very hot objects such as the sun. Detected b the eye and photographic film. Used in optical fibre communication
Gamma ray
Produced in the nuclei of radioactive elements. Used in medical diagnosis and therapy. Dangerous in high doses since ionising.
Infrared
All hot objects produce infrared radiation. Used in burglar alarms, night vision goggles and optical fibre communication
Microwave
Used for rapid heating in microwave oven, sending signals between satellites and the Earth, radar imaging
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General waves properties
Amplitude: the height of the wave, measured in meters.
Wavelength: the distance between adjacent crests, measured in meters.
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Period: the time it takes for one complete wave to pass a given point, measured in seconds.
Frequency: the number of complete waves that pass a point in one second, measured in inverse seconds, or Hertz (Hz).
Speed: the horizontal speed of a point on a wave as it propagates, measured in meters / second.
Light
Refraction
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change in direction of propagation of any wave as a result of its travelling at different speeds at different points along the wave front.
Thin converging lens
Any optical lens that is thicker in the middle than at the edges will make parallel light rays converge to a point, and is called converging lens.
Reflection
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the throwing back by a body or surface of light, heat, or sound without absorbing it.
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