Electromagnetic Radiation

Electromagnetic Waves Changing electric and magnetic fields can transmit energy across empty space Energy produced is electromagnetic radiation

Speed, Wavelength, and Frequency of EM Radiation c (speed of light) = 3.00 x 10 8 m/s c = λf as wavelength increases, frequency decreases and vice versa

The Electromagnetic Spectrum Range of wavelengths Logarithmic scale because it spans such a large range of values

Radio Waves Radio, television, cell phones Transducers—convert sound into electrical signals FM—frequency modulated (shorter) AM—amplitude modulated

Microwaves Telecommunication—satellites Microwave oven

Infrared Radiation Thermal radiation –Electric heater –Infrared thermometer –Remote control

Visible Light Eyes detect these waves ROYGBIV White light—mixture of all of the colors of the visible spectrum See color when that wavelength is reflected

Ultraviolet Radiation Sunlight Ozone molecules absorb most Water purifiers Sterilizing instruments

X Rays High energy Medicine Airport security

Gamma Rays Produced by nuclear reactions and by radioactive nuclei Medical uses

The Photoelectric Effect Photons—bundles of energy Planck’s constant –Energy of a photon is proportional to the frequency of the electromagnetic radiation. Planck’s constant is that proportionality. –h = x J s –E photon = h c/λ

The Photoelectric Effect Work function –The energy required to “break” an electron out of a metallic surface—Φ Hf = Φ + KE e –Photon energy (speed of light/wavelength) = work function + kinetic energy