EM waves

Gamma rays

• produced when there are changes to nuclei of atoms

• when emmited, nuclear energy stored in nucleus decreases

• used in medical imaging, radiotherapy as they can damage and penetrate body tissues

X - rays

• produced by rapid deceleration of free electrons

• pass easily through soft body tissue but absorbed by bone

• used in medical imaging and treatment

Ultra violet

• causes sunburn, skin cancer, blindness

• used in fluorescence, which can absorb ultraviolet radiation, then emit longer wavelength visible light

• thus used in energy saving light bulbs and security ink

High frequency hazard

• gamma rays, x rays and ultraviolet are all high frequency

• the energy they deposit within body can ionise atoms that make up cells

• leading to mutations to cells which can lead to cancer

radiation dose

• unit of dose is sievert (Sv)

• 1000 mSv = 1Sv

• average person in uk recieved 2.7mSv from all sources of background radiation

Visible light

• Used in human sight

• lasers

• fibre optic commutations

• recieved from natural sources and artifical sources

Visible spectrum

Red, orange, yellow, green, blue, indigo, violet

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Infrared

• also called thermal radiation

• used in electrical heaters, cookers

• infrared cameras

Microwaves

• used in cooking food, mobile phone networks

• Satellite combinations, bluetooth

• Microwaves are used for satellite communications as they can easily pass thought the earth’s atmosphere

Radio waves

• Used for ground based radio and television signals

How are radio waves produced?

• an alternating current flows through a transmitter antenna

• the AC makes electrons oscillate

• as electrons accelerate as they change direction, they create changing electric fields

• changing electric fields produce changing magnetic fields

• these continuously generate eachother and move away from antenna

• this energy travels through space as a radio wave