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General Properties of Light

General Properties of Light. Light as a wave Speed Wave properties: wavelength, frequency, period, speed, amplitude, intensity Electromagnetic wave. EM Spectrum. Diffraction – the bending of waves at an aperture or obstacle. Double-slit pattern of water/sound waves. I peak =4I o.

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General Properties of Light

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  1. General Properties of Light Light as a wave Speed Wave properties: wavelength, frequency, period, speed, amplitude, intensity Electromagnetic wave

  2. EM Spectrum

  3. Diffraction – the bending of waves at an aperture or obstacle

  4. Double-slit pattern of water/sound waves

  5. Ipeak=4Io y q D Iaverage=2Io Interference – double-slit, speckle

  6. Polarization

  7. Light as a particle • Photon • Energy packet • Photoelectric effect • Double slit- revisited

  8. Double Slit Experiment with Electrons Reducing intensity of the light, so that only one electron arrives at the slits at a time Detections come in lumps = quanta Intensity exhibits interference

  9. Questions? Why do no electrons (or photons) ever arrive at some locations? Clearly How can we get interference when only 1 particle at a time is going through the slits? What does that particle interfere with? Suppose we actually check which slit each particle went through and know with certainty – what happens then? How can this be? Resolution comes from QED with Feynman

  10. Electron diffraction

  11. How is light produced? • Chemical energy - fire • Electrical energy - lightning • Nuclear energy - stars • Incandescent • Electric discharge – continuous vs discrete spectrum • Fluorescence

  12. Special Properties of Laser Light • Monochromatic • Intense • Pencil beam – collimated • Coherent • Can be cw or pulsed

  13. Prototype Laser • Energy levels • Absorption, spontaneous emission • Stimulated emission • Population inversion • Metastable state • Pump – optical, electron excitation, atom-atom collisions, chemical • Resonant cavity – gain, cavity modes, beam

  14. Types of Lasers • 3-level vs 4-level • Ruby, first, a 3-level pulsed laser • He-Ne, gas, 4-level

  15. Argon ion, gas

  16. CO2 – molecular gas laser • Neodymium – solid-state

  17. Diode laserDye – liquid laser

  18. Laser Applications • Communications • Coding information, fiber optics

  19. Medical uses

  20. Materials processing • Science

  21. Laser Tweezers

  22. Holography

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