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AP Physics Chp 29

AP Physics Chp 29 . Wave-Particle Theory (Duality) Interference patterns by electrons. Blackbody E=nhf n=0,1,2,…. Quantized h= 6.626 x 10 -34 Js. Photons E=hf “packet” of energy Photoelectric Effect.

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AP Physics Chp 29

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  1. AP Physics Chp 29

  2. Wave-Particle Theory (Duality) • Interference patterns by electrons

  3. Blackbody • E=nhf n=0,1,2,…. Quantized • h= 6.626 x 10-34 Js

  4. Photons E=hf • “packet” of energy • Photoelectric Effect

  5. The minimum amount of energy needed to remove an electron from a metal surface by “light” is the work function Wo • hf = KEmax + Wo

  6. Photons only have KE and no rest mass • Use of photoelectric effect • Dig Cameras and Safety Devices

  7. Momentum of photons? • Compton Effect • X-ray scatters electrons and reflects itself

  8. hfincident photon= hf’photon + KEelectron • Momentum of photon p= h/λ • Wavelenth Shift • λ’ – λ = (h/mc) ( 1-cosθ) • λ’ is the scattered photon

  9. The work function for Gold is 3.9 eV ( 1ev=1.6x10-19J ) • What is the minimum frequency of “light” that will eject an electron?

  10. Wo = 3.9eV x 1.6x10-19 J/eV =6.24x10-19 J • hf = KE + Wo KE = 0 for the minumum • hf = Wo • f = Wo / h = 6.24x10-19 J / 6.626 x 10-34 Js • f = 9.4x1014 1/s

  11. de Broglie Wavelength • λ= h/p • λ= h/mv

  12. Heisenberg Uncertainty Principle • (∆p)(∆y) ≥ h/(4π) • (∆E)(∆t) ≥ h/(4π)

  13. What is the wavelength of a baseball (0.145 Kg) thrown at 44.7 m/s? What about an electron traveling 0.8c?

  14. λ= h/mv • = 6.626x10-34 Js / (0.145Kg)(44.7m/s) • = 1.02x10-34 m

  15. λ= h/mv • = 6.626x10-34 Js / (9.11x01-31Kg)(0.8c) • = 3.05x10-12 m

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