GREPhysics.NET: GR8677 #32

GR8677 #32

Problem

GREPhysics.NET Official Solution

Quantum Mechanics $\Rightarrow$ }Photoelectric Effect

(A) The photoelectric effect was derived before formal quantum mechanics and that angular momentum mess came along. Moreover, electron orbits don't really apply to the valance electron sea.

(B) This is true, but it doesn't help derive the photoelectric effect.

(C) Nah, there's also something weird called electron-electron annihilation. Basically, two electrons crash into each other and a photon is created. (Perhaps some other particles, too.) Also, think of your regular desktop lamp---light is emitted, but the electrons are probably not jumping between orbits.

(D) Right. Einstein won the Nobel Prize about a hundred years ago via his proposal that photons have quantized energy $E=h\nu$ .

(E) As a pure-ideal theory, the photoelectric effect depends on a single photon exciting a single electron. It favors the particle view of light. Choice (E) is out.

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Comments

blue_down_quark
2008-08-22 06:00:53

There's no such thing as electron-electron annihilation AFAIK. If it existed all the atoms in the universe would turn into nuclei and radiation (losing their electrons).
But there's an interaction called electron-positron annihilation.

FortranMan
2008-10-19 16:04:17

Plus the wording is too broad for (C), it could be just as well be a valence electron between atoms.

russian
2017-08-12 13:55:10

Charge would not be conserved in e-e- -> gamma. But yes, e+e- -> gamma is common (pair production). There are questions related to the pair production energy on the pGRE

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