photoelectric effect question

mihir23

For the photoelectric effect, when light hits a metal, and the frequency is above the work function, electrons are given off.

I am curious if the metal becomes more and more positive if this happens. i.e oxidation without reduction??.

For this question, assume that it is done in a empty vacuum and thus the meal cant take electrons from anything else

Bonasa

1) I am curious if the metal becomes more and more positive if this happens.
Right. But there is Coulomb force that slows and stops escaped electrons and they can't go to the infinite. But as frequency goes higher kinetic energy of escaped electrons is higher and positive charge accumulates more effective.
2) i.e oxidation without reduction??
I think no, coz there are no single atoms in metal as i.e. in any chemical solution. Atoms have collective electron cloud. Or it's possible to call oxidation of hole speciment not atom.
3) For this question, assume that it is done in a empty vacuum and thus the meal cant take electrons from anything else
4) If u have enough energy for electrons to break through Coulomb barier (and big volume of vacuumed space) than electrons move to infinite and u have positive charged piece of metal

M Quack

1) In principle yes. The metal will loose electrons and the potential will increase until the work function+potential = photon energy and no more electrons are emitted.

Usually one does not want this to happen during such an experiments. Therefore the metal is connected to ground so that electrons are replenished and the potential is kept constant. It is possilbe to measure the current going from the metal to ground, and this is frequently done.

2) There is no oxidisation in the chemical sense. In a metal, it is not meaningful to assign an ionic charge to the atoms.

3) Correct.