What happens when a particle meets its corresponding antiparticle?

They annihilate, converting their combined mass entirely into energy in the form of photons.

What is pair creation?

The process where a photon of sufficient energy converts into a particle–antiparticle pair, with the photon energy becoming the mass and kinetic energy of the particles.

In pair creation, what happens to the energy of the original photon?

It is converted into the rest mass energy and kinetic energy of the particle–antiparticle pair produced.

Why must the minimum photon energy for pair creation equal 2m₀c² rather than just m₀c²?

Because pair creation produces both a particle and its antiparticle, each with rest mass m₀, so the total rest mass energy required is twice that of a single particle.

OCR A-Level Physics A H556

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Nuclear and Particle Physics

Annihilation, mass defect and binding energy

4 things to know
Papers 1, 2 and 3

Overview

Recall questions on annihilation and pair creation, the minimum photon energy for pair creation, mass defect, binding energy and the steps of calculating binding energy.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Numbers

State the equation that relates binding energy to mass defect.

Key term

In particle–antiparticle annihilation, what form does the released energy take?

Key term

What is the minimum photon energy required for pair creation, expressed in terms of the particle's rest mass?

Key term

When calculating the binding energy of a nucleus, what nuclear composition must first be determined?

Questions from this subtopic

Each one with the model answer underneath.

1
What happens when a particle meets its corresponding antiparticle?
Model answer
They annihilate, converting their combined mass entirely into energy in the form of photons.
2
In particle–antiparticle annihilation, what form does the released energy take?
Model answer
Photons (electromagnetic radiation).
3
What is pair creation?
Model answer
The process where a photon of sufficient energy converts into a particle–antiparticle pair, with the photon energy becoming the mass and kinetic energy of the particles.
4
In pair creation, what happens to the energy of the original photon?
Model answer
It is converted into the rest mass energy and kinetic energy of the particle–antiparticle pair produced.
5
What is the minimum photon energy required for pair creation, expressed in terms of the particle's rest mass?
Model answer
E = 2m₀c², which is twice the rest mass energy of the particle being created.
6
Why must the minimum photon energy for pair creation equal 2m₀c² rather than just m₀c²?
Model answer
Because pair creation produces both a particle and its antiparticle, each with rest mass m₀, so the total rest mass energy required is twice that of a single particle.

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