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the electromagnetic spectrum (EM waves (all em waves transfer energy e.g.…
the electromagnetic spectrum
EM waves
all em waves transfer energy e.g. microwaves transfer energy from source to food or sun or sun emits energy to earth
they are all transverse waves
they all travel at the same speed in a vacuum - 300,000,000m/s
(longest wavelength/lowest freq)RADIO-MICRO-INFRARED-VISIBLE LIGHT-ULTRAVIOLET-XRAYS-GAMMARAYS(shortest wavelength/highest frequency)
our eyes can only detect visible light
do not need particles to move
materials interact with EM waves differently depending on wavelength - glass transmits visible light, reflects/absorbs UV/IR
relationships
as wavelength decreases, frequency increases
as frequency increases, energy of wave increases
danger of the em spectrum
higher frequency EM waves have more energy, so exposure can transfer too much energy to cells, causing them to mutate or potentially damage them/causing cancer
microwaves - internal heating of body cells
infra red - skin burns
ultraviolet - damage to surface cells and eyes, leading to skin cancer
X-ray/gamma ray - mutation or damage to cells in body
uses of the em spectrum
radio - communications, satellite transmission. they can be produced by oscillations in electrical circuits, or they can induce oscillations in electrical circuits
microwave - cooking, communication
infra-red - cooking, thermal imaging, short range communication, optical fibres
visible light - vision, photography, illumination
ultraviolet - security marking, fluorescent lamps, disinfecting water
X-ray - observing internal structure of objects, airport/medical scanners
gamma ray sterilising food/medical equipment, treating cancer
temperature
all bodies emit radiation, the higher the temperature, the more wavelengths will be emitted
must radiate same avg power it absorbs to remain at constant temp
absorbs more power than it emits, temp increases. absorbs less power than it emits - temp decreases
temperature of the earth is maintained by amount of energy received and emitted from the sun
most reaches the atmosphere, but some is reflected by the atmosphere
energy is absorbed the re-emitted as longer wavelength IR radiation
short wavelength IR radiation from sun reaches the earth
mostly absorbed by the atmosphere (greenhouse gases,CO2 etc) and keeps earth warm