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Wave/Particle Duality. Question: What happens if we repeat Young’s double slit experiment with a beam of electrons (particles) instead of light? Answer:

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Presentation on theme: "Wave/Particle Duality. Question: What happens if we repeat Young’s double slit experiment with a beam of electrons (particles) instead of light? Answer:"— Presentation transcript:

1 Wave/Particle Duality

2 Question: What happens if we repeat Young’s double slit experiment with a beam of electrons (particles) instead of light? Answer: We still get an interference pattern!! Why? All particles exhibit “wave-like” properties!!!!!

3 DeBroglie Wavelength λ = h/p h = 6.63x J*s What is the DeBroglie wavelength of an electron moving at v = 3.5x10 6 ?

4 What is the DeBroglie wavelength of a baseball (m = 0.15kg) moving at v = 13m/s?

5 Question: If particles can act like waves can waves act like particles? Answer: Yes!!!! (PhotoElectric effect, Compton Scattering)

6 Photoelectric Effect Einstein won his Nobel prize for it. He realized that light is made up of packets of energy (photons) When light shines on a metal surface it can eject electrons from the metal, but only if the frequency is high enough. Higher frequency means higher energy per photon. E = h f

7 Photoelectric Effect hf = k E max + W o Each photon emits one electron Higher frequency means the electron is emitted with more KE (velocity). If the minimum frequency is used KE = 0. Higher Intensity means more overall energy but if the frequency is not great enough no electrons are ejected. Higher intensity means more photons which can eject more electrons, but can’t give individual electrons more energy.

8 What is the work function of a metal that requires a min. wavelength of 485nm to eject electrons from its surface?

9 What is the velocity of an electron ejected by light of frequency 1.5x10 15 Hz from a metal with a work function 4.1x J?


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