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p5 (order (radio waves : 1 - 10^4m, microwaves : 10^-2m, infrared : 10^-5m…
p5
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health
radio waves transmitted through body, not absorbed
some microwaves are absorbed, heats cells which can be dangerous
infrared and visible light mostly reflected or absorbed by the skin, causes heating, IR can cause burns
UV absorbed by skin, high frequency, transfers more, causes more damage, collides with atoms in living cells, may knock off electrons and cause ionising radiation, can cause genetic mutation and cancer
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EM waves
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transfer energy from source to absorber, higher frequency transfers more energy
medical imaging
x rays
mostly transmitted by tissues, some absorption varies between tissues
lots can produce high resolution images in 2D and 3D of soft and hard tissues, CT scans
gamma rays
transmitted by skin, soft tissue and bone
if produced inside body, can be detected
radiotracers swallowed or injected, gamma rays detected and force an image, can see how the body is working
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microwaves
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food microwaves penetrate a few cms before being absorbed and transferring energy to water molecules in food which heat up
water molecules transfer energy to other food molecules
light signals
communication using optical fibres, carry data over long distances as pulses of light
bounce light off narrow core, pulse of light enters core at certain angle and is reflected until it emerges at other end
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ultraviolet
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can cause damage to DNA in skin cells, important to wear sunscreen
x rays
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directed through the object or body onto detector place
bright parts where fewer x rays get through
exposure can cause cell damage