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because i always forget :(
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what is an electromagnetic wave
transverse wave caused by changing magnetic and electrical fields
as you go down the spectrum, wavelength decreases and frequency increases
therefore wave speed is always the same 330m/s in air
radio waves
uses
used in communication and broadcasting
can be long wave (diffracts round curve of earth)
can be medium wave (reflects of ionosphere)
can be short wave (bluetooth)
an alternating current in a transmitter produces a radio wave, which is absorbed by electrons in a receiver, which then alternate and create an alternating current with the same frequency as the radio wave.
microwaves
uses
satellite communication
travels easily through earth’s watery atmosphere
heating
microwaves transfer thermal energy to water molecules in food, heating it
dangers
can heat body cells
infrared radiation
uses
ir is given out by all hot objects
heating
ir is thermal energy so can be used in electrical heaters which transfer ir and therefore heat
cooking
ir is thermal energy so can be used in toasters which have a heating element that transfers ir (heat) to food
dangers
too much exposure to ir can cause skin burns and even skin cancer
visible light
uses
fibre optic cables
transfers data over a long distance in cables with glass lining on inside, that reflect light, and cause the light to bounce back and forth through the cable, without it being scattered or absorbed
taking photos and videos
cameras are set up to detect visible light
ultraviolet
uses
fluorescent lights
fluorescent materials absorb uv and emit it as visible light. fluorescent lights produce uv, and are an energy efficient light source
security INK
BECAUSE IT FLUORESCES WHEN UV IS SHONE ON IT
TANNING
dangers
skin burns and skin cancer
x-rays
uses
medical imaging
x rays can pass through tissue but not bone, so when x rays are shone onto a body, the xrays that pass through are detected and produce a negative image, showing where bones are
radiotherapy
in high doses x rays can kill cells, so they can be directed at some cancerous cells, and they will kill them (also kill surrounding healthy cells)
dangers
ionise atoms in body cells, which can cause mutations is DNAf, that can lead to cancer
gamma rays
uses
medical tracers
a gamma source can be put in the body, and then detected from outside the body, as gamma can pass through tissue
radiotherapy
in high doses gamma rays can kill living cells, so they can be directed at cancerous cells to kill them, but will also kill surrounding bodily cells
can sterilise medical tools
high energy and kill bacteria
dangers
can ionise atoms in bodily cells, leading to mutations in DNA, which can cause cancer