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Light

Light. Wave Particle Duality. Light travels as a wave and a stream of particles, called photons. The duality of light was not accepted until the 1900’s Waves- transverse, not mechanical because it does not require a medium Photons- bundle of electromagnetic energy Move at the speed of light

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Light

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  1. Light

  2. Wave Particle Duality • Light travels as a wave and a stream of particles, called photons. • The duality of light was not accepted until the 1900’s • Waves- transverse, not mechanical because it does not require a medium • Photons- bundle of electromagnetic energy • Move at the speed of light • Have no mass

  3. Double-Slit Experiment(1801- Thomas Young) • A beam of light was passed through a thin card with 2 pinholes cut side by side • If light traveled as a particle, there would be 2 light patterns, but Young found it produced a barcode pattern due to interference because it behaves like a wave Double Slit Experiment

  4. Light as a Wave • Quantum Theory • 1900- Max Planck • Black box experiment • Shined UV light into a hole inside a black box • If light was a wave, no light would get out and would produce an infinite amount of UV radiation • Box instead radiated different colors • Light must carry energy in discrete quantities • Led to photoelectric effect • Photoelectric Effect • 1905- Albert Einstein • Shined UV light onto a metal surface • Detected electrons being emitted from the surface • If the energy in light comes in bundles, then one can think of light containing tiny lumps, or photons • When photons strike the metal surface, they transfer their energy to electrons, which become dislodged from their “parent” atoms

  5. Electromagnetic wave • Electromagnetic waves are formed when an electric field combines with a magnetic field at a perpendicular angle. • The natural vibrations of these fields (which look something like a sin(x) equation) then interact and in doing so, induce each other to move.

  6. EM Spectrum • The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation.

  7. EM Spectrum

  8. Source: radio waves are produced by an alternating current in a tuned electrical circuit. Use: communication technology, AM/FM radio, TV. Higher frequency radio waves can carry more information per time unit than lower ones and are used for TV’s whereas the low frequency radio waves are used for traditional radio stations. Radio Waves

  9. Source: Microwaves are produced by oscillations of electrons in a vacuum as well as when certain semi-conductors, such as water, get excited. Uses: cooking food, cell-phones, short-range internet links, radar, and traffic cameras. They are known to cause cataracts as well. Microwaves

  10. Source: Infrared waves are produced by a change in the rotational and vibrational kinetic energies of electrons in the atoms of heated bodies. The hotter the object the more infrared radiation it emits. Uses: remote controls, night vision technology, and weather forecasting, and to capture images of far away objects in space. Infrared Waves

  11. Source: Visible light can be generated by the re-arrangement of outer orbital electrons in molecules, when electrons emit light and other forms of electromagnetic radiation as they lose energy. Visible light is detected by stimulating the nerve endings of the retina of the human eye and with rods and cones. Use: TO SEE!! Visible Spectrum…. ROY G BIV Visible Light

  12. Source: high energy electron transitions, and our sun. Uses: production of vitamin D and melanin (tanning pigment in skin), to ionize atoms and kill bacteria. These waves can cause some items to fluoresce and give you skin cancer. Ultraviolet (UV) Waves

  13. Source: the rapid deceleration of fast moving electrons upon striking a metal target or by the sudden change in energy of the innermost orbital electrons in atoms. X-rays are also given off by stars. X-Rays have a relatively high penetrating power that increases as the density of the object its attempting to penetrate decreases (an inverse relationship) and increases as the frequency of the X-ray increases toward the Gamma end of the spectrum (a direct relationship). Uses: In the medical field to see inside of people’s bodies, in airport security systems, and to detect objects far-away in outer space that emit X-Rays but are too far away to be seen with visible light. X-Rays

  14. Source: Gamma Rays are produced by objects in outer space such as supernova explosions and regions around black holes. On Earth they are the result of radioactive decay and nuclear explosions. Use: to kill targeted cancerous cells in “Radiotherapy.” Gamma Rays

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