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# class26 - Exam 2 Announcements Reading for Monday 6.8 6.10...

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Exam 2 Announcements Reading for Monday: 6.8 – 6.10 Today’s class: More about electron interference and “wave functions” Double-slit experiment D { r 1 r 2 θ H L bright bright bright We found: H = L λ D But λ ~ 0.2 nm H is too small to see unless D ~1 nm! If we use protons instead of electrons (assume protons were going at same speed as electrons were), what happens to the Q1 A. increases B. stays the same C. decreases D. Can‘t tell. Need to do the experiment. e # e - scatt. angle θ 50 0 0 See a peak!! The angle at which we detect most electrons is determined by interference of deBroglie waves! (probability related to wave function) Davisson and Germer and Clinton-- VERY clean nickel crystal. Interference is electron scattering off Ni atoms. e e e e e e e e det. Ni Observe pattern of scattering electrons off atoms Looks like …. a Wave! Phased array antenna for the “Patriot” missile guiding radar. (Patriot: Phased array track to intercept of target) Cool research @ CU: Prof. Zoya Popovich, ECEE

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λ =h/p, h = 6.6 x 10 -34 J s, θ = λ /D = (h/p)(1/D) # e’s scatt. angle θ 50 0 0 See peak!! Ni e e e e e e θ Q2 Radical idea, want to check as carefully as possible. What else does deBroglie wave idea predict that we can check? If increase energy, what will peak do? a. get larger b. get smaller c. shift to smaller angle d. shift to larger angle e. same angle but get wider Davisson-Germer Diffraction Warning: For qualitative use only. This is near-field view Modern evidence of matter waves: Double-slit experiment with
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class26 - Exam 2 Announcements Reading for Monday 6.8 6.10...

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