The work function for platinum is 6.35 eV. Ultraviolet light of wavelength 150 n
ID: 2019170 • Letter: T
Question
The work function for platinum is 6.35 eV.Ultraviolet light of wavelength 150 nm is incident on the
clean surface of a platinum sample. We wish to predict the
stopping voltage we will need for electrons ejected from
the surface. (a) What is the photon energy of the ultraviolet
light? (b) How do you know that these photons will
eject electrons from platinum? (c) What is the maximum
kinetic energy of the ejected photoelectrons? (d) What
stopping voltage would be required to arrest the current of
photoelectrons?
Explanation / Answer
work function W = 6.35 eV.
wavelength = 150 nm
(a) the photon energy of the ultraviolet light
E = hc/ = 8.27 eV
(b) How do you know that these photons will
eject electrons from platinum?
Because E > W
(c) the maximum kinetic energy of the ejected photoelectrons
KE = E - W = 1.92 eV
(d) stopping voltage would be required to arrest the current of photoelectrons
= KE/e = 1.92 V
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