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The Compton Effect

The Compton Effect. EMR 2. Review of Photoelectric Effect: Intensity Matters. - the greater the intensity/brightness, the greater the photoelectric current Because . . . . One photon emits one electron Dim light – 3 photons hit metal and emit 3 electrons

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The Compton Effect

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  1. The Compton Effect EMR 2

  2. Review of Photoelectric Effect: Intensity Matters • - the greater the intensity/brightness, the greater the photoelectric current • Because . . . . One photon emits one electron • Dim light – 3 photons hit metal and emit 3 electrons • Bright light – 5 photons hit metal and emit 5 electrons so . . . there is a greater photoelectric current

  3. Robert Millikan • Irradiated different substances with different frequencies of radiation to determine fo

  4. Graphs Slope = h fo W 1. Energy vs frequency Current vs frequency

  5. Graphs 3. Current vs Intensity 4. Current vs Stopping Voltage

  6. Wave Particle Duality Theory Theory indicates that particles can behave as waves and waves can behave as particles. To describe the photoelectric effect, light or radiation is described as a wave and can be considered a particle because it has energy Energy is a particle-like property

  7. Compton Effect • Einstein predicted that photons should also possess momentum (particle like property) Two equations that describe the momentum of photons making no reference to mass

  8. Examples • Determine the momentum of a a. Photon of wavelength 250 nm b. Electron moving at 4.00 x 105 m/s

  9. Scattered x-ray Incident beam Graphite or carbon atom Compton (1922) – indicated experimentally that photons have momentum • directed x-rays at graphite (carbon) atoms and detected the scattered rays

  10. the energy and momentum gained by the electron within the atom equals the energy and momentum lost by the photon • the results obey the laws of conservation of energy and momentum • Compton Effect – the scattering of an x-ray by an electron resulting in a reduced frequency of the x-ray (increase in wavelength)

  11. e Scattered x-ray • Compton showed how the change in wavelength ( ) of the scattered photon is related to the angle at which the x-ray is scattered • Momentum of an x-ray (EMR)

  12. Speed of light Mass of scattering electrons Equation • Energy and momentum are conserved, so the collision is elastic Angle of scattered photon Change of wavelength of photon

  13. Eg) Determine the maximum change in wavelength of a 0.050 nm x-ray scattered by an electron(maximum scattering is at 180⁰ where the photon bounces back) • ( occurs when 1 – cosθ is a maximum value at θ = 180⁰)

  14. Eg) An x-ray photon with a wavelength of 0.0150 nm scatters at 60.0⁰ after contacting an electron. Determine the wavelength of the scattered photon.

  15. http://www.kcvs.ca/site/projects/physics.html

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