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Published byEvelyn Cooke Modified over 4 years ago

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Some issues in Science?

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Pluto

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Duck-Billed Platypus

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Duck-billed Beaver tailed Egg laying Venemous Webbed feet Electroreception Babies drink milk with no nipples!

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Viruses

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Solid or liquid?

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Language

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A real issue?

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Electrons – waves or particles?

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Einstein In 1905 Einstein showed that the photoelectric effect could be understood if light were thought of as a stream of particles (photons) with energy equal to hf. I got my Nobel prize for that.

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Louis de Broglie (in 1923) If light can behave both as a wave and a particle, I wonder if a particle can also behave as a wave?

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Louis de Broglie Ill try messing around with some of Einsteins formulae and see what I can come up with.

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I can imagine a photon of light. If it had a mass of m p, then its momentum would be given by p = m p c where c is the speed of light.

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Now Einstein has a lovely formula that he discovered linking mass with energy (E = mc 2 ) and he also used Plancks formula E = hf. What if I put them equal to each other? mc 2 = hf

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So for my photon m p = hf/c 2 So if p = m p c = hf/c

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p = m p c = hf/c Now using the wave equation, c = fλ (f = c/λ) So m p c = hc/λc = h/λ λ = h p

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So youre saying that a particle of momentum p has a wavelength equal to Plancks constant divided by p?! Yes! λ = h/p It will be known as the de Broglie wavelength of the particle

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Confirmation of de Broglies ideas De Broglie didnt have to wait long for his idea to be shown to be correct. In fact in 1929 I received a Nobel prize for my prediction of the wave nature of the electron.

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Interference patterns

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Electron interference

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They know were watching!

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Schrödingers cat

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Physics 1202: Lecture 31 Today’s Agenda Announcements: Extra creditsExtra credits –Final-like problems –Team in class HW 9 this FridayHW 9 this Friday.

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