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Introductory Physics Homework Help
Maximum kinetic energy / cutoff potential problem
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[QUOTE="chef99, post: 6009754, member: 639309"] [h2]Homework Statement [/h2] [B]Light with a wavelength of 630nm is directed at a metallic surface that has a work function of 1.5 eV. Find:[/B][B]a) The maximum kinetic energy of the emitted electrons. b) The cutoff potential required to stop the photoelectrons.[/B] [h2]Homework Equations[/h2] E[SUB]k[/SUB] = hc / λ - W E[SUB]k[/SUB] = eV[SUB]o[/SUB] [h2]The Attempt at a Solution[/h2] a) λ = 630nm = 6.3 x10[SUP]-7[/SUP]m W = 1.5eV (1.60x10[SUP]-19[/SUP]J/eV) W = 2.4 x10[SUP]-19[/SUP]JE[SUB]k[/SUB] = hc / λ - W E[SUB]k[/SUB] = (6.63 x10[SUP]-34[/SUP]J)(3.0 x10[SUP]8[/SUP]m/s) / (6.3 x10-7m) - 2.4 x10[SUP]-19[/SUP]JE[SUB]k[/SUB] = 7.57 x10[SUP]-20[/SUP]J The maximum kinetic energy is 7.57 x10[SUP]-20[/SUP]J.b) E[SUB]k[/SUB] = eV[SUB]o[/SUB] 7.57 x10[SUP]-20[/SUP]J = (1.60 x10[SUP]-19[/SUP]) V[SUB]o[/SUB] V[SUB]o[/SUB] = 7.57 x10[SUP]-20[/SUP]J / (1.60 x10[SUP]-19[/SUP]) V[SUB]o[/SUB] = 0.47 V The cutoff is 0.47 V. I am uncertain if my answer to part a) is correct, I have reviewed all my steps and can't find an error, however, for all of the questions I have done so far, the answer has always been x10[SUP]-19[/SUP], whereas my answer here, is 7.57 x10[SUP]-20[/SUP]J is x10[SUP]-20[/SUP]. Is this an acceptable answer? Is it possible for it to not always be to the [SUP]-19[/SUP]J? or did I make an error somewhere in my calculations? [/QUOTE]
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Maximum kinetic energy / cutoff potential problem
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