Is this an annihilation process , I am so confused now
A positron with a kinetic energy of 2.0 keV collides with an electron at rest, creating two photons that have equal energy.
Show that the energy of each photon is 8.2 × 10−14 J.
Show that the energy of each photon is 8.2 × 10−14 J.
pair production.
Why do you said so? Particles and Anti-particles meet each other and converted their mass into a pair of gamma ray photons (Original post by Luqman.ldn)pair production
(edited 5 years ago)
Yea thats right, but I am not sure why the rest mass of electron has to double?
Total energy = 2keV + 2 × 511 keV = 1024 keV✔
= 1024 × 1.6 × 10−19 = 1.64 × 10−13J✔
Energy of each photon = 1.64 × 10−13/2 = 8.19 × 10−14 (J) ✔
Total energy = 2keV + 2 × 511 keV = 1024 keV✔
= 1024 × 1.6 × 10−19 = 1.64 × 10−13J✔
Energy of each photon = 1.64 × 10−13/2 = 8.19 × 10−14 (J) ✔
Original post by NicolasLee
Yea thats right, but I am not sure why the rest mass of electron has to double?
Total energy = 2keV + 2 × 511 keV = 1024 keV✔
= 1024 × 1.6 × 10−19 = 1.64 × 10−13J✔
Energy of each photon = 1.64 × 10−13/2 = 8.19 × 10−14 (J) ✔
Total energy = 2keV + 2 × 511 keV = 1024 keV✔
= 1024 × 1.6 × 10−19 = 1.64 × 10−13J✔
Energy of each photon = 1.64 × 10−13/2 = 8.19 × 10−14 (J) ✔
Yeah I have no idea. The only reason I could think of for doing that is if the total energy of the positron equals its kinetic energy PLUS its rest energy, but I don't remember ever seeing that anywhere.
Original post by nzy
Yeah I have no idea. The only reason I could think of for doing that is if the total energy of the positron equals its kinetic energy PLUS its rest energy, but I don't remember ever seeing that anywhere.
I probably figured it out why this is a pair production because this process is required kinetic energy but not for annihilation.
Original post by Luqman.ldn
pair production.
Wrong. Pair production is when a photon is converted into a particle and an antiparticle. The process described in the OP is indeed annihilation, as a particle (the electron) is colliding with an antiparticle (the positron), converting their rest energies and kinetic energies into photons.
Original post by NicolasLee
I probably figured it out why this is a pair production because this process is required kinetic energy but not for annihilation.
what
The total energy before the interaction is equal to the total energy after the interaction, as per the law of conservation of energy.
So the energy before impact is given by the mass of the electron at rest (multiplied by c2 ), the mass of the positron (again multiplied by c2) plus the kinetic energy of the positron.
So the energy before impact is given by the mass of the electron at rest (multiplied by c2 ), the mass of the positron (again multiplied by c2) plus the kinetic energy of the positron.
(edited 5 years ago)
Original post by Sinnoh
The total energy before the interaction is equal to the total energy after the interaction, as per the law of conservation of energy.
So the energy before impact is given by the mass of the electron at rest, the mass of the positron plus the kinetic energy of the positron.
So the energy before impact is given by the mass of the electron at rest, the mass of the positron plus the kinetic energy of the positron.
Wow many thanks!
Original post by Sinnoh
Wrong. Pair production is when a photon is converted into a particle and an antiparticle. The process described in the OP is indeed annihilation, as a particle (the electron) is colliding with an antiparticle (the positron), converting their rest energies and kinetic energies into photons.
Yeah , my bad. Covered it during the summer so I forgot which way round it is.
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