Answer
0.8 eV; No electrons would be ejected.
Work Step by Step
The work function may be found from the given information. A photon energy of 6.0 eV yields electrons with a stopping potential of 3.8 V, i.e., electrons with a maximum KE of 3.8 eV.
From equation 27-5a, we see that the work function is 6.0 eV – 3.8 eV = 2.2 eV.
Suppose that the photons’ wavelength were doubled. The photon energy is halved, from 6.0 eV to 3.0 eV. The maximum kinetic energy of ejected electrons is now 3.0 eV – 2.2 eV = 0.8 eV.
Now suppose that the photons’ original wavelength were tripled. The photon energy is cut by a factor of 3, from 6.0 eV to 2.0 eV. This is less than the work function, so no electrons are ejected.
