A photon of wavelength 250 nm ejects an electron from a metal. The ejected elect
ID: 1988456 • Letter: A
Question
A photon of wavelength 250 nm ejects an electron from a metal. The ejected electron has a deBroglie wavelength of 0.85 nm.a. Calculate the kinetic energy of the electron.
b. Assuming that the kinetic energy found in (a) is the maximum kinetic energy that it could have, calculate the function of the metal.
c. The incident photon was created when an atom underwent an electronic transition. On the energy level diagram of the atom below, the transition labeled X corresponds to a photon wavelength of 400 nm. Indicate which transition could be the source of the original 250 nm photon by circling the correct letter. Justify your answer.
Explanation / Answer
Given Wavelength of incident photon = 250 nm = ( 250 nm ) ( 10 -9 m / 1 nm ) = 250 * 10 -9 m Debroglie wave length of ejected electron ' = 0.85 nm = ( 0.85 nm ) ( 10 -9 m / 1 nm ) = 0.85 * 10 -9 m a) Momentum of electron is p = h / ' = ( 6.625 *10-34 Js ) / ( 0.85 * 10 -9 m ) = 7.794*10-25 kg.m/s Kinetic energy of electron is K = p 2 / 2 m = ( 7.794*10-25 kg.m/s ) 2 / 2 ( 9.11 *10-31 kg ) = 3.334 *10-19 J = 2.08 eV = 2.08 eV _______________________________________________________ b) Energy of incident photon is E = h c / = ( 6.625 *10-34 Js ) ( 3 *108 m/s ) / ( 250 * 10 -9 m ) = 7.95*10-19 J = 4.96 eV Work function of metal is W = E - K = 4.96 eV - 2.08 eV = 2.88 eV _______________________________________________________ Please post one question per one post _______________________________________________________ Please post one question per one postRelated Questions
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