The cutoff wavelength for a metal is found to be 505 nm. (a) Calculate the work

Question

The cutoff wavelength for a metal is found to be 505 nm.
(a) Calculate the work function for this metal.
eV


(b) The metal is illuminated by light of wavelength 480. nm.Calculate the maximum kinetic energy of the emitted electrons.
eV


(c) Express this energy in joules.
J


(d) Calculate the maximum velocity of the emitted electrons.
m/s

Explanation / Answer

a) work function : W = E(photon) = hfo = hc/o = hc/eo (in eV) => W = 6.63x10^-34*3x10^8/(1.6x10^-19*505x10^-9) = 2.46eV b) Maximum kinetic energy : Kmax = hf - W = hc/e - W = 6.63x10^-34*3x10^8/(1.6x10^-19*480x10^-9)- 2.46 = 0.128 eV c) Kmax = 0.128 eV = 0.128*1.6x10^-19 J = 2.05x10^-20 J d) velocity : Kmax = (1/2)mV^2 =>   V = (2Kmax/m) = 2.12x10^5 m/s

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