Section: Science

152) View Additional Information

Consider the following results, obtained using 5.0 eV photons and the same photocell that is discussed in the passage.

Table
Relative intensity of light	Electrical current (mA)	Maximum kinetic energy of ejected electron (eV)
low	28	3.1
medium	42	3.1
high	58	3.1

The maximum kinetic energy of the ejected electron, 3.1 eV, was not the expected value. The expected value was:

1. 0.0 eV
2. between 0.1 eV and 0.8 eV
3. between 0.9 eV and 2.9 eV
4. greater than 3.0 eV

According to the passage, the maximum kinetic energy an ejected electron can have is the photon's energy minus the metal's work function. In Trials 4–6, the energy per photon was 4.0 eV and the maximum kinetic energy of the electrons ejected from the metal was 0.9. In Trials 7–9, the energy per photon was 6.0 eV and the maximum kinetic energy of the electrons ejected from the metal was 2.9. Thus, the work function was 3.1 eV. If 5.0 eV photons were directed at the metal, the maximum kinetic energy of an ejected electron would be the photon's energy minus the work function: 5.0 eV minus 3.1 eV, or 1.9 eV.