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Wave-Particle Duality

Wave-Particle Duality. Electromagnetic radiation -- wave properties and particle properties. Principle of Complementarity. To understand any given experiment, use either the wave or the photon theory, but not both.

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Wave-Particle Duality

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  1. Wave-Particle Duality

  2. Electromagnetic radiation -- wave properties and particle properties

  3. Principle of Complementarity To understand any given experiment, use either the wave or the photon theory, but not both. Not possible to visualize the “true” nature of light (EM radiation).

  4. EM SPECTRUM Low frequency (radio, microwaves) – WAVES High frequency (x-rays, gamma rays) – PARTICLES Middle frequency (visible light) – WAVES/PARTICLES

  5. Waves: v = λf v = c = 3.00 x 108 m/s Energy is continuous; depends on amplitude of wave

  6. Bremsstrahlung (braking radiation) x-ray Decelerated electron emits radiation If electron loses all its energy  max frequency photon

  7. Bremsstrahlung: “braking radiation” Nucleus slows down the electron. Decelerated electron emits energy as an x-ray photon.

  8. K-shell capture High-speed electron knocks K-shell electron out of orbit. When outer-shell electron fills gap, it emits x-ray

  9. x-ray tube operated at 50 kV shortest-wavelength x-ray photon emitted? KE = eV E = hf = hc/λ 2.5 x 10-11 m

  10. MOMENTUM OF A PHOTON Matter particles: p = mv Energy particles: p = h/λ

  11. PARTICLES AS WAVES Waves (energy) have particle properties. wave properties. Particles (matter) have 1924 – de Broglie wavelength: λ = h/p p = mv

  12. Wavelength of a person A 75 kg-boy runs at 9.0 m/s. What is his wavelength? λ = (6.626 x 10-34)/(75 x 9.0) = 9.8 x 10-37 m Too small to be detected!

  13. Wavelength of an electron An electron is accelerated across 100 V. Wavelength? λ = h/√(2eVm) 1.2 x 10-10 m Size of atom ~ 10-10 m MEASURABLE !

  14. Davisson-Germer (1927) Electrons produce an interference (diffraction) pattern. Electrons have wave properties. Conclusion:

  15. Wave-particle duality also applies to material objects Principle of Complementarity also applies to matter What is an electron?

  16. b) 1.408 x 10-14 m c) 4.706 x 10-20 kg m/s d) 8.08 x 10-14 J

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