SAT Subject Physics Practice Question 349: Answer and Explanation
45. A photon can eject an electron from the surface of a photovoltaic metal if and only if
A. the frequency of the photon is above the activation minimum.
B. the wavelength of the photon is above the activation minimum.
C. the speed of the photon is above an activation minimum.
D. the momentum of the photon is below the activation minimum.
E. the momentum of the impacted electron is above the activation minimum.
Correct Answer: A
The correct answer is (A). Electrons in photovoltaic metals are only energized by the photons that carry enough energy to dislodge the electrons.