Antiparticles
Antiparticles
- Every particle has a corresponding antiparticle. The mass stays the same and the charge changes sign.
Same mass, opposite charge
Definition
2 marksWhat is meant by antiparticle?
Model answer: A particle with the same mass as the corresponding particle but the opposite charge.
- Every particle has a matching with the same mass and the opposite charge. The antiparticle of the electron is the positron.
- An antiproton is three antiquarks: anti-u, anti-u, anti-d. Its charge is , the opposite of the proton. (9702/21/M/J/25 Q7(b)) (9702/23/M/J/25 Q8)
- When a particle meets its antiparticle they annihilate: both disappear and their mass becomes energy, given out as gamma photons.
Your turn9702/23/O/N/24 Q7
A particle is made of one up quark and one anti-down quark. What type of particle is it, and what is its charge? (9702/23/O/N/24 Q7) (9702/23/M/J/24 Q6(c))
Show worked answer
Answer: one quark and one antiquark is a meson. Its charge is .
Common mistake
An antiquark flips the sign of the charge and keeps the size. An anti-up is , not . Change the sign, keep the fraction.