Electromagnetic Spectrum Range of Behavior Electromagnetic waves are

Electromagnetic Spectrum

Range of Behavior ] Electromagnetic waves are characterized by their wavelength or frequency. • Linked by the speed of light ] The frequency is associated with an energy. • High frequency is high energy ] The common unit is the electron-volt (e. V). • Work done by 1 V potential on one electron hc = 1. 240 ke. V nm

Electromagnetic Radiation ] Traditional upper boundaries for types of EM radiation: Radio waves Microwaves Infrared Visible light Ultraviolet light X-rays Gamma rays l (m) 1 1 10 -3 0. 75 10 -6 0. 4 10 -6 1. 2 10 -8 1. 4 10 -11 n (Hz) E (e. V) 3 108 1. 24 10 -6 3 1011 1. 24 10 -3 4 1014 1. 65 7. 5 1014 3. 1 2. 4 1016 1 102 3 1019 1. 2 105 (highest energy)

Radio Waves ] Radio waves primarily come from the oscillation of currents in conductors. ] A 1 MHz frequency has an energy of 6. 6 x 10 -28 J. ] The long wavelengths travel easily and are not interfered by atoms. • Except conductors

Microwaves ] Microwaves are very short wavelength radio waves. ] Microwaves are associated with the vibrations of some atoms and molecules. ] Water molecules act as a dipole. • Motion increased by microwaves • Causes heating

Radiation from Heat ] Heated objects give off electromagnetic waves. • Higher temperature has more radiation ] A hot object gives off a spectrum of frequencies. intensity low energy high energy • Shifts based on temperature ] This is called blackbody radiation frequency

Infrared ] Wavelengths longer than visible light are called infrared rays. • Come from warm objects ] Molecules are heated by infrared waves. • Radiant heat

Visible Light ] Visible light is radiation in a narrow band of wavelength. • 400 nm to 800 nm • Narrower ranges are colors ] Corresponds to maximum output from the Sun. intensity low energy high energy ] Many atoms and molecules have specific behavior at unique frequencies of light. frequency

Ultraviolet ] Ultraviolet rays have shorter wavelengths than visible light. • Higher energy • Often with visible light ] Some molecules absorb ultraviolet and reemit visible light. • Fluorescent light

X-Rays ] X-rays are associated with energetic transitions in atoms. electrons target ] Continuous spectra result from electron bombardment. ] The short wavelength x-rays can penetrate materials. • Stopped by dense atoms x-ray

Gamma Rays ] Gamma rays are photons associated with nuclear or particle processes. • Energy range overlaps: soft gamma equals hard x-ray g e e Z ] Acceleration of a very energetic charged particle gives x-rays and gamma rays. • Called bremsstrahlung next