Problem

• Light strikes a sodium surface and causes photoelectric emission. If Vstop = 5.0 volts and the work function ? is 2.2 eV, what is the wavelength of the light?

• Ephoton = hf = hc/?

• Kmax = Ephoton - ? = hc/? - ? = e Vstop

• ? = (hc)/(e Vstop + ? )

• h = 6.63x10-34 J.s = 6.63x10-34 /1.6x10-19 eV.s = 4.14 x10-15 eV.s

• ? = (4.14 x10-15 eV.s)(3x108m/s)/[5.0 eV+2.2 eV] =170 nm

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