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Questions and Answers
What is the minimum energy required for a photon to produce an electron-positron pair?
What is the minimum energy required for a photon to produce an electron-positron pair?
Why must a massive object, such as a nucleus, participate in the pair production process?
Why must a massive object, such as a nucleus, participate in the pair production process?
What is the inverse process of pair production?
What is the inverse process of pair production?
Why do positrons not last long in nature?
Why do positrons not last long in nature?
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What is the recoil energy of the nucleus approximately equal to?
What is the recoil energy of the nucleus approximately equal to?
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What is the condition for energy conservation in pair production?
What is the condition for energy conservation in pair production?
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What is the result of an electron and a positron colliding?
What is the result of an electron and a positron colliding?
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Why can a photon not produce an electron or a positron alone?
Why can a photon not produce an electron or a positron alone?
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What is the energy of the recoil nucleus approximately equal to?
What is the energy of the recoil nucleus approximately equal to?
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What is the process where a photon interacts with a nucleus to produce an electron-positron pair?
What is the process where a photon interacts with a nucleus to produce an electron-positron pair?
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Study Notes
Pair Production and Annihilation
- The collision of a positron with an electron produces a hydrogen-like atom called positronium, with a mean lifetime of about 10^(-10) s.
- Positronium is similar to a hydrogen atom, where the proton is replaced by a positron.
Pair Production
- Pair production occurs when a high-energy photon passes through a foil, resulting in the creation of an electron-positron pair.
- The process requires the interaction of the photon with an external field, such as the Coulomb field of an atomic nucleus, to conserve momentum.
- The energy of the incident photon (h) must be greater than the sum of the rest masses of the electron and positron (2m_ec^2) to conserve energy.
Minimum Energy for Pair Production
- The minimum energy of a photon required for pair production can be calculated using the equation: h = 2m_ec^2.
Relativistic Quantum Mechanics
- Dirac's relativistic quantum mechanics predicts the existence of the positron, the antiparticle of the electron, with the same mass and opposite charge.
- The positron was discovered by Anderson in 1932, four years after its prediction by Dirac's theory.
Pair Annihilation
- The inverse of pair production is pair annihilation, where an electron and a positron collide and annihilate each other, producing electromagnetic radiation.
- This process explains why positrons do not last long in nature, as they eventually get annihilated after colliding with an electron.
Conditions for Pair Production and Annihilation
- Charge, momentum, and energy conservation are required for pair production and annihilation to occur.
- A massive object, such as a nucleus, must participate in the process to take away some of the photon's momentum.
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Description
Explore the properties of positronium, a hydrogen-like atom formed by a positron and electron collision, and learn about pair annihilation processes. Understand how energy and momentum are conserved in these processes.
