the electromagnetic spectrum

because i always forget :(

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