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Unformatted text preview: P a g e | 1 ‐ 3 Physics 143 Fall Term 2007 HOMEWORK 4 Due: September 24 Problem 1: (BFG Ch.4 Problem 2) Chemical processes typically involve energies on the order of 1eV. What, then, is the typical wavelength of electromagnetic radiation emitted in the course of chemical reactions? Nuclear processes involve energies on the order of 1MeV. Where in the spectrum of electromagnetic radiation are the photons that may be emitted in a nuclear reaction? We know that, E ൌ h f ൌ hc λ λ ൌ hc E For chemical processes λ ୡ ൌ h c E ൌ 6.63 ൈ 10 ିଷସ J · s ൈ 2.99 ൈ 10 ଼ m/s 1eV ~10 ି m ൌ 1µm For nuclear processes, since Energy is 10 times greater, the wavelength will be 10 ି times smaller, λ ୬ ~10 ିଵଶ m ൌ 1pm Problem 2: (BFG Ch.4 Problem 7, 9) 7. By doubling the intensity of his monochromatic light source, an experimenter hopes to increase the speed of the photoelectrons emitted by a given sample of metal. Will the experimenter succeed? What, if anything, will change in the resulting emission of photoelectrons? No, the speed will not increase. We have the formula: 1 2 m ୣ v ଶ ൌ hf െ W Doubling the intensity doesn’t change the frequency(energy) of the lights source in the formula....
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