Sunday, February 13, 2011

Mastering Physics: Photoelectric Effect

Photoelectric Effect The following table lists the work functions of a few common metals, measured in electron volts.
Metal \Phi\,({\rm eV})
Cesium 1.9
Potassium 2.2
Sodium 2.3
Lithium 2.5
Calcium 3.2
Copper 4.5
Silver 4.7
Platinum 5.6
Using these data, answer the following questions about the photoelectric effect.

Part A
Light with a wavelength of 190 \rm nm is incident on a metal surface. The most energetic electrons emitted from the surface are measured to have 4.0 \rm eV of kinetic energy. Which of the metals in the table is the surface most likely to be made of?


Part B
Of the eight metals listed in the table, how many will eject electrons when a green laser (\lambda_{\rm g} = 510\; \rm nm) is shined on them?


Part C
Light with some unknown wavelength is incident on a piece of copper. The most energetic electrons emitted from the copper have 2.7 \rm eV of kinetic energy. If the copper is replaced with a piece of sodium, what will be the maximum possible kinetic energy K of the electrons emitted from this new surface?

  K  = 4.9
  \rm eV