Answer to Question #200366 in Physics for Lee Zabat

Question

The work functions for three metals X, Y. and Z are 4, 5, and 6 eV, respectively. Photoelectrons are created when UV light shines on these metals. The photoelectrons from which metal would have the largest stopping voltage?

A. Z

B. Y

C. X

Answer 1

According to Einsten's photoelectric equation, we have:

$$KE_{max}=eV_s=E-\phi_0,$$

here, $KE_{max}$ is the maximum kinetic energy of the emitted photoelectrons, $E$ is the energy of the incident photons of UV light, $\phi_0$ is the work function of the metal, $e$ is the charge of the photoelectrons and $V_s$ is the stopping potential.

Energy of the incident photons of UV light is the same for all three metals. Therefore, the kinetic energy of the emitted photoelectrons will be maximum for the metal with the least work function (metal X, $\phi_0=4\ eV$). The greater the kinetic energy of the emitted photoelectrons, the greater is the stopping voltage. Thus, photoelectrons from metal X would have the largest stopping voltage.

The correct answer is C.