Ch. 17 ELECTROMAGNETIC SPECTRUM

Electromagnetic waves  Are made of changing electric and magnetic fields  EM waves DO NOT need a medium to travel  Are made of changing electric and magnetic fields  EM waves DO NOT need a medium to travel

Electromagnetic Radiation  The energy transferred by EM waves is called electromagnetic radiation

Electromagnetic Spectrum  All EM waves travel at the same speed, but have different wavelengths and frequencies.

Communication waves  Radio waves have the longest wavelengths and the lowest frequency

Microwaves are most commonly used in microwave ovens. They are also used to transmit cellular calls

 Radar is used to find objects or detect the speed of objects

Infrared Rays  Infra is Latin for “below”. Infrared means “below red”  Sometimes called thermal or heat rays  Infra is Latin for “below”. Infrared means “below red”  Sometimes called thermal or heat rays

Visible Light  The only waves that can be seen are visible light  red, orange, yellow, green, blue, indigo, violet (ROY G BIV)  The only waves that can be seen are visible light  red, orange, yellow, green, blue, indigo, violet (ROY G BIV)

Ultraviolet (UV) Rays  Ultra is Latin for “beyond” Ultraviolet means “beyond violet”  Carry more energy than visible light  Can damage or kill living cells  We need UV rays to produce vitamin D  Too much exposure can cause skin cancer and damage the eyes  Ultra is Latin for “beyond” Ultraviolet means “beyond violet”  Carry more energy than visible light  Can damage or kill living cells  We need UV rays to produce vitamin D  Too much exposure can cause skin cancer and damage the eyes

X-rays  Can penetrate most soft matter  Used to make images of bones  Too much exposure can cause cancer  Can penetrate most soft matter  Used to make images of bones  Too much exposure can cause cancer

Gamma Rays  Shortest wavelength and highest frequency  Can cause serious illness, but when used in controlled conditions, can be used to kill cancer cells  Shortest wavelength and highest frequency  Can cause serious illness, but when used in controlled conditions, can be used to kill cancer cells