Consider the photoelectric effect. The minimum energy required to remove an elec

Question

Consider the photoelectric effect. The minimum energy required to remove an electron is known as the work function (it is like an ionization energy for an atom). Label the work function W. (a) Derive a formula for the maximum kinetic energy an electron possesses if it is kicked off the surface by an incoming photon of frequency ?>?0. What is the threshold frequency in terms of W? (b) The work function for cesium is 2.14 eV. What is the longest wavelength that can eject an electron from cesium? c) What are the maximum kinetic energy and the speed of electrons emitted when the metal is irradiated with light of 300 nm?

Explanation / Answer

a) E = W + KE ; KE = Max possible Kinetic Energy

KE = E - W

KE = h(v - vo) ; v and vo are the frequency of incident photon and that corresponding to work function respectively.

b) hc/lambda = 2.14 ev = 2.14*1.6*10^-19

Lambda = 580 nm

c) E = hc/lambda = hc/300nm = 4.136 eV

W = 2.14 eV

KE max = E-W = 1.996 eV

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