Chapter 17 The Electromagnetic Spectrum I. The Nature of Electromagnetic Waves

Electromagnetic energy is all around us. Where does it come from???

It comes from the sun.

Electromagnetic Waves n The sun is producing an enormous amount of energy all the time. This energy pours off the sun as electromagnetic waves and rays. The different wavelengths determine the type of wave or ray it is.

Electromagnetic Waves n Transverse waves that have electric and magnetic properties. –Consist of changing electric & magnetic fields

Transverse waves that have electric and magnetic properties. Consist of changing electric & magnetic fields

ELECTROMAGNETIC SPECTRUM

Radio Waves Radio Waves n Have the longest wavelength and lowest frequencies. – Frequency ( Hz) 10 6 to 10 4 – Wavelengths (m) to 10 6

Radio Waves n Microwaves- (radio waves) shortest wavelengths and highest frequencies. – Can pass through glass and plastic. –Metals reflect microwaves. –Frequency ( Hz) to 10 6 – Wavelengths (m) to 10 -1

Radio Waves n Radar- Radio Detecting and Ranging. –Used to detect objects. –Used in military planes, ships and installations. –Safety - do not walk in front of airplane with radar on.

Radio Waves n Radar is actually microwaves. n Doppler – used for weather and police –Sometimes used in sport events.

Radio Waves n Magnetic Resonance Imaging –(M.R.I) –used for lots of medical purposes n like brain and spine disorders.

Infrared Rays n Felt as Heat - wavelengths a little shorter than visible light. – Have higher frequencies and shorter wavelengths than radio waves. –Frequency ( Hz) to – Wavelengths (m) to 10 -4

Visible Light n Shorter wavelengths and higher frequencies than infrared rays – Shortest wavelengths are violet or purple. color color n The only part of the spectrum we can see. –Frequency ( Hz) – Wavelengths (m) 10 -7

Ultraviolet Light n Electromagnetic wavelengths shorter than visible light. – Used to to treat jaundice for newborns. – Over exposure can cause skin cancer. –Frequency ( Hz) to – Wavelengths (m) to 10 -7

X-Rays n Electromagnetic waves with very short wavelengths – Can penetrate most matter. – Over exposure can cause cancer. – Used to see bones and structures. –Frequency ( Hz) to – Wavelengths (m) to 10 -9

Gamma & Cosmic Rays n Shortest wavelengths and highest frequencies on the electromagnetic spectrum. – Can kill some cancer cells. – Frequency ( Hz) to – Wavelengths (m) to