Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I've been learning about photoelectricity. An electron can gain the energy from a single photon, and if that energy is greater than the work function of the metal the electron can leave the metal. However I was under the impression that the electrons in the metal are responsible for holding the nuclei in the metal together?

Surely if the metal is exposed to light, where the photons have more energy than the work function, for long enough (or very intense light), all/majority of the electrons will leave the metal and no longer be holding the nuclei together.

Also will the work function increase with time, as there are less and less electrons, so the ratio of positive nuclei to negative electrons increases and the electrons are more attracted to the nuclei, so more energy is required to break that attraction?

(addtionally, how come the photoelectric effect is not noticed in daily life, with metals becoming positively charged just by being in light?)

share|cite|improve this question
What happens to the bulk charge state of the metal after this has been going on for a while? How does that affect the process? – dmckee May 10 '12 at 21:14
@dmckee, I don't understand your comment? – Jonathan. May 10 '12 at 21:15
I'm asking you to quantify the effect that you ask about in the third paragraph. You're on the right track already, just follow through with the thought. – dmckee May 10 '12 at 21:20
@dmckee, I mean will the energy an electron needs to be emitted, increase as the number of electrons in the metal decreases? – Jonathan. May 10 '12 at 21:32
@Jonathan: Yes, because the metal will become positively charged, and suck the electrons back in. – Ron Maimon May 11 '12 at 5:39
up vote 4 down vote accepted

Metals do disintegrate in light, just very slowly. Light is often a very weak source and its effect is quite unnoticeable. There are many systems that use highly concentrated light beams, lasers, for etching purposes. Note, however, that as electrons are removed, it becomes roughly exponentially harder to remove them as the material becomes positively charged. It is very unlikely in any process for a significant portion of electrons to be removed without removing the nuclei.

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.