Take Home Quiz 3

Physics 43 Quiz 5 Fall 2016
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50 points. Show work for any credit. Box final numerical answers in 3 Sig figs. Neatness counts!
1. A metal having a work function of 2.8 eV is illuminated with monochromatic light whose photon energy
is 3.9 eV. What is the threshold frequency for photoelectron production?
2. How fast must a nonrelativistic electron move so its de Broglie wavelength is the same as the wavelength
of a 3.4-eV photon?
3. Light of wavelength 105 nm falls on a metal surface for which the work function is 5.00 eV. What is the
minimum de Broglie wavelength of the photoelectrons emitted from this metal?
4. A nonrelativistic electron is accelerated from rest through a potential difference. After acceleration
the electron has a de Broglie wavelength of 880 nm. What is the potential difference though which this
electron was accelerated?
5. ) Calculate the kinetic energy (in eV) of a nonrelativistic neutron that has a de Broglie wavelength of
9.9 × 10-12 m.
6. The Figure shows the stopping potential versus the incident
photon frequency for the photoelectric effect for sodium. Use the
graph to find (a) the work function in eV, (b) the cutoff wavelength
in nm. Compare the work function you find to the value in the table
or found online. The data are taken from R. A. Millikan, Phys. Rev.
7:362 (1916).
7. The following table shows data obtained in a photoelectric
experiment for a material. (a) Using these data, plot KE vs
wavelength in excel. Do a linear fit. From the graph, determine
(b) an experimental value for Planck’s constant (in joule-seconds)
and a percent error with the accepted value. (c) the work function
(in electron volts) for the surface. (d) Find the cut off frequency.
Can you identify the material? Show your work here and final
answers here. Attach your excel plot.

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