A photocathode whose work function is 2.5 eV is illuminated with white light that has a continuous wavelength band from 360 nm to 700 nm.The stopping potential for this white light illumination is closest to:
A)0.94 V
B)0.85 V
C)1.0 V
D)1.1 V
E)1.2 V

Question

Quizplus · Accepted Answer

The stopping potential is determined by the maximum kinetic energy of the emitted electrons, which is given by the difference between the photon energy and the work function. The shortest wavelength (360 nm) corresponds to the highest energy photons. Using the formula $E = \frac{hc}{\lambda}$, the photon energy is approximately 3.45 eV. Subtracting the work function (2.5 eV) gives a maximum kinetic energy of about 0.95 eV, which corresponds to a stopping potential of approximately 0.94 V.

A Photocathode Whose Work Function Is 2