Conservation of Energy/momentum in Photoelectric process

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Homework Help Overview

The discussion revolves around the conservation of energy and momentum in the context of the photoelectric effect, specifically addressing the claim that a free electron cannot absorb a photon while conserving both quantities. The original poster references a textbook problem and presents an argument regarding the rest energy of a moving electron.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to demonstrate that energy and momentum cannot be conserved in the interaction between a free electron and a photon, questioning the validity of their argument based on the rest energy of the electron. Some participants question the logical connection between the premises and the conclusion drawn by the original poster.

Discussion Status

The discussion is ongoing, with participants exploring the initial argument and seeking clarification on how to approach the problem. Guidance has been offered to start by writing the relevant conservation equations, indicating a potential direction for further exploration.

Contextual Notes

The original poster's argument relies on specific assumptions about the nature of energy and momentum conservation in particle interactions, which are currently under scrutiny. There may be constraints related to the definitions and conditions of the photoelectric effect being discussed.

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Homework Statement



Show that a free electron cannot absorb a photon and conserve both energy and momentum in the process. Hence, the photoelectric process requires a bound electron. (Eisberg and Resnick 2nd Ed)

Homework Equations



hv = E
p = K / c
E2 = (pc)2 + (m0c2)2

The Attempt at a Solution



I've simply shown since
E2 = (pc)2 + (m0c2)2,

rest energy of a moving electron isn't zero and thus energy and momentum cannot be conserved. Is this argument true/suffice?
 
Last edited:
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I don't see how the conclusion follows from the premise, and I suspect you don't either since you asked if the argument was true.
 
How/where then should I start?
 
Start by writing the equations for the conservation of energy and momentum the electron and photon would have to satisfy.
 

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