38 deBroglie

38 deBroglie - Craig Ogilvie Logistics On-line course...

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Unformatted text preview: Craig Ogilvie Logistics On-line course evaluation (ClassClimate) Available till Monday 8am finals week Greener solution + saves staff time typing comments Feedback is vital Please respond Craig Ogilvie 11 Craig Ogilvie Summary Lecture 37 Two distinct, far point sources, can you tell their images apart ? if large qob, two separate diffraction peaks each image is not a point but a diffraction pattern,width qD q o b D Two images formed on screen near focus of converging lens move two sources closer smaller qob, e.g. image of second source sits at diffraction minimum of first still smaller ob cannot resolve two separate diffraction peaks Craig Ogilvie Goal Introduction to quantum physics Photon: energy transported by light comes in finite, small amounts Wave characteristics of all moving objects Craig Ogilvie 33 Craig Ogilvie Craig Ogilvie 44 Photoelectric Effect: pre-lecture video + Tue rec. - = hf hf KE electron , max for all materials slope of the line is always Plancks constant, h=6.626 10-34 Js f is the work function depends on material Interpretation (Einstein) all the energy of photon (E=hf) given to electron during collision costs some energy (work function f) for electron to leave atoms Electrons emitted when light shines on metal Craig Ogilvie Craig Ogilvie 55 Question: Increase brightness, 1st round If the frequency f is below cut-off, increase brightness of light What happens is . 1. electrons escape from metal because increasing intensity, increased strength of E-field, larger acceleration of electrons => escape from atom 2. photon still has same energy, there are more single photon- electron collisions but each has insufficient energy to knock electron out of atom => no electrons knocked out 53 of 340 Craig Ogilvie Craig Ogilvie 66 Question: Increase brightness, 2nd round 6% 94% 13% 87% 1 2 If the frequency f is below cut-off, increase brightness of light...
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This note was uploaded on 09/20/2011 for the course PHYS 222 taught by Professor Johnson during the Spring '07 term at Iowa State.

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38 deBroglie - Craig Ogilvie Logistics On-line course...

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