In the photoelectric effect, electrons are never emitted from a metal if the frequency of the incoming light is below a certain threshold value. This is because:
a. The number of photons in low-frequency light is too small to eject electrons.
b. Photons of lower-frequency light don't have enough energy to eject an electron.
c. The electric field of low-frequency light does not vibrate the electrons rapidly enough to eject them.
d. Low-frequency light does not penetrate far enough into the metal to eject electrons.
