Conservation of Energy and Momentum in Photon-Electron Interactions

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SUMMARY

The discussion focuses on the conservation of energy and momentum in photon-electron interactions, specifically when a photon strikes a stationary electron, resulting in the creation of an electron-positron pair. The energy of the initial photon is determined to be 4mc², where m represents the mass of the electron. Key concepts include the necessity of applying both momentum and energy conservation principles, as well as accounting for relativistic effects during the interaction. The positron, being an antiparticle, shares the same mass as the electron, which is crucial for calculating the final mass of the system.

PREREQUISITES
  • Understanding of conservation laws in physics, specifically momentum and energy conservation.
  • Familiarity with relativistic physics and its implications on particle interactions.
  • Knowledge of particle-antiparticle pairs, particularly electrons and positrons.
  • Basic grasp of the concept of mass-energy equivalence, expressed as E=mc².
NEXT STEPS
  • Study the principles of relativistic momentum and energy conservation in particle physics.
  • Learn about the creation of particle-antiparticle pairs in high-energy photon interactions.
  • Explore detailed examples of photon-electron interactions and their outcomes.
  • Investigate the implications of mass-energy equivalence in various physical scenarios.
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the dynamics of particle interactions, particularly in the context of high-energy physics and quantum mechanics.

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Homework Statement


A photon strikes an electron of mass m that is initially at rest, creating an electron-positron
pair. The photon is destroyed and the positron and two electrons move
off at equal speeds along the initial direction of the photon. The energy of the
photon was ?

The Attempt at a Solution

are we suppose to use momentum conservation?

or kinetic energy conservation?

do we have to factor in relativistic effects?

the answer is 4mc2

but i have totally no idea at all how to get that

i think the final mass = 1.5 m ? where m = electron mass

because positron and electron pair = 0.5 m , then add in the other stationary electron so 1.5m ?

this is confusing . greatly appreciate any help thanks!
 
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I haven't worked it out myself, but see if you can first. You know that momentum is conserved and energy is conserved (or at least I'm telling you that it is a valid strong interaction that conserves energy if you don't know). You should use relativistic effects.

No idea what you are talking about with masses. The positron has the same mass as the electron, they are anti-particles.
 
oh ok. will try it. thanks!
 

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