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Antiparticles

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Antiparticles

Antimatter is matter that is made of antiparticles. These are particles with the same characteristics as matter but with the opposite charge. Every component of matter at an atomic level has an antiparticle, except for photons. If the symbol of a proton is p, its antiparticle symbol will be , and this is true for neutrons and neutrinos but not for electrons whose symbol is .

The discovery of antimatter

Paul Dirac first theorised antiparticles, but the first to discover an antiparticle was Carl Anderson when he found the antiparticles of an electron, also named positrons.

Antiparticles. Particle accelerator cern. StudySmarterFigure 1. The ELENA system is used to trap antiprotons. Source: Ryan Bodenstein, Flickr (CC BY 2.0).

What is an antiparticle?

Antiparticles are the blocks that make antimatter. There is an antiparticle for every subatomic particle in the nucleus and orbit of an atom. Protons, neutrons, neutrinos, and electrons all have antiparticles. The characteristics of antiparticles are similar to particles; they just differ in their charge. Antiparticles can be created by radioactive decay processes in the atom. They can also interact with matter, leading to an annihilation process.

See the following table of particles and antiparticles:

ParticleProtonNeutronElectronNeutrino
symbolpn
AntiparticleAntiprotonAntineutronpositronAntineutrino
symbol

Characteristics of antiparticles

Antiparticles and particles have the same mass and energy at rest; the only difference is their charge. The charge of a positron is 1.6022 * 10 ^ -19C, which is the opposite of an electron charge, which has a value of -1.6022 * 10 ^ -19C. The same occurs with protons, which have a positive charge for normal matter and a negative charge for the antiproton.

Particle and antiparticle annihilation

When matter and antimatter interact, they destroy each other. This destruction has three main characteristics:

  • The particles masses are destroyed.
  • The destruction converts all the mass of the particles into energy.
  • The energy is released in the form of high energy photons.

Antiparticles. Antimatter-matter annihilation. StudySmarterFigure 2. When matter and antimatter collide, this produces an annihilation event that results in photons being released. Source. Manuel R. Camacho, StudySmarter.

Antimatter and matter pair creation

In some cases, a photon can interact with a particle, which creates a pair of particles. The event is accordingly named pair creation, and the pair consists of a particle and its antiparticle.

Energy must be conserved during pair creation. A photon has a certain amount of energy (X), and the energy of the two particles created (Y and Z) must be equal to the total energy of the photon that created them. The conservation of energy is expressed more simply below:

Calculating the energy released by matter and antimatter

To calculate the energy of the impact between matter and antimatter, we need to obtain the total energy of the photon released during the collision. This energy is a relationship between the light velocity c, the Planck constant h, and the photons wavelength λ. The formula to calculate this is as follows:

Here is a simple example:

Calculate the energy released by a collision between a particle and an antiparticle.

The photon released by the collision has a wavelength of 0.005 nanometres. To calculate the released energy, you need to convert the number of nanometres to metres. One nanometre is equal to 1⋅10 ^ -9 metres, so you need to multiply 0.005 by 1⋅10 ^ -9 metres:

Now you need to multiply the approximate velocity of light in the vacuum by the Planck constant h, which has a value of 6.63 * 10 ^ -34J / s:

Then you need to divide this by the wavelength of the released photon. The results are expressed in the energy units joules (J):

Antiparticles - key takeaways

  • Antiparticles are particles that have the opposite charge to normal particles.
  • Antimatter is matter made of antiparticles.
  • The mass of particles and antiparticles is the same, but their electrical charge is the opposite.
  • When matter and antimatter collide, they destroy each other and create energy in the form of photons.

Frequently Asked Questions about Antiparticles

An antiparticle is a particle that has the same mass but the opposite charge to a particle.

No, photons do not have antiparticles.

An antiproton.

Final Antiparticles Quiz

Question

What is antimatter?

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Answer

Antimatter is matter made of antiparticles.

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Question

What is an antiparticle?

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Answer

An antiparticle is the opposite of a particle, with the same mass but the opposite charge.

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Question

Does an antiparticle have the same charge as its particle?

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Answer

No, it has the opposite charge.

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Question

Do particles and antiparticles have the same mass?

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Answer

Yes, they do.

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Question

Do particles and antiparticles have the same energy at rest?

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Answer

Yes, they do.

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Question

What is the symbol of an antiproton?

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Answer

.


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Question

Who theorised antiparticles?

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Answer

Paul Dirac.

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Question

Who discovered the first antiparticle?

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Answer

Carl Andersen.

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Question

What happens when matter and antimatter collide?

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Answer

They annihilate each other.

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What happens to the mass of matter and antimatter when they collide?

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Answer

It gets destroyed.

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What happens to the mass of the particles after antimatter-matter annihilation?

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Answer

It converts to energy.

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Are photons part of the energy released after antimatter-matter annihilation?

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Answer

Yes, they are.

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Question

Can a photon create antimatter?

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Answer

Yes, after the photon interacts with a particle.

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Question

What is the name of the event that creates antimatter?

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Answer

Pair creation.

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Question

Does the energy released by a matter and antimatter collision depend on the photons released?

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Answer

Yes, it depends on the photon’s wavelength.

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Question

What is the velocity of light in a vacuum?

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Answer

300,000,000 m/s.

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Question

Which units does photon energy use?

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Answer

Joules (J).

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Question

Does a neutron have an antiparticle?

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Answer

Yes, the antineutron.

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Question

Does the electron have an antiparticle?

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Answer

Yes, the antielectron or positron.

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Question

What is another name for an antielectron?

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Answer

Positron.

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