Electromagnetic Spectrum

Range of Behavior  Electromagnetic waves are characterized by their wavelength or frequency. Linked by the speed of lightLinked by the speed of light  The frequency is associated with an energy. High frequency is high energyHigh frequency is high energy  The common unit is the electron-volt (eV). Work done by 1 V potential on one electronWork done by 1 V potential on one electron hc = keV nm

Electromagnetic Radiation  Traditional upper boundaries for types of EM radiation:  (m)  (Hz)E (eV) Radio waves 13   Radio waves 13   Microwaves1    Microwaves1    Infrared0.75   Infrared0.75   Visible light0.4   Visible light0.4   Ultraviolet light1.2    10 2 Ultraviolet light1.2    10 2 X-rays1.4    10 5 X-rays1.4    10 5 Gamma rays (highest energy) Gamma rays (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 J.  The long wavelengths travel easily and are not interfered by atoms. Except conductorsExcept 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 radiationHigher temperature has more radiation  A hot object gives off a spectrum of frequencies. Shifts based on temperatureShifts based on temperature  This is called blackbody radiation low energy high energy frequency intensity

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

Visible Light  Visible light is radiation in a narrow band of wavelength. 400 nm to 800 nm400 nm to 800 nm Narrower ranges are colorsNarrower ranges are colors  Corresponds to maximum output from the Sun.  Many atoms and molecules have specific behavior at unique frequencies of light. low energy high energy frequency intensity

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.  Continuous spectra result from electron bombardment.  The short wavelength x-rays can penetrate materials. Stopped by dense atomsStopped by dense atoms target electrons x-ray

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