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Learn about electromagnetic radiation, from the speed, wavelength, and frequency of EM waves to the diverse spectrum including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. Discover practical applications like telecommunication, medical imaging, and the photoelectric effect.
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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 108 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 = 6.626176 x 10-34 J•s • Ephoton = h•c/λ
The Photoelectric Effect • Work function • The energy required to “break” an electron out of a metallic surface—Φ • Hf = Φ + KEe • Photon energy (speed of light/wavelength) = work function + kinetic energy