Particles Flashcards
What is meant by specific charge?
The charge per unit mass of an atom - Specific charge=Charge/Mass - Unit: C/kg
What is the letter associated with the proton number?
Z
What is a nucleon?
A constituent of the nucleon: a proton or a neutron
What letter represents nucleon number?
A
What is an isotope?
A form of an element that has the same number of protons but a different number of neutrons
What is a use of radioactive isotopes?
Carbon dating - the proportion of Carbon-14 in a material can be used to estimate its age
What is the strong nuclear force?
The fundamental force that keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons
What is the range of the strong nuclear force?
Repulsive up to 0.5fm,
Attractive between 0.5fm and 3fm,
Negligible past 3fm
What makes a nucleus unstable?
Nuclei which have either too many of either protons, neutrons, or both
How do nuclei with too many nucleons decay?
Alpha decay (emission of a helium nucleus formed of 2 protons and 2 neutrons)
How do nuclei with too many neutrons decay?
Beta minus decay (a neutron decays to a proton by the weak interaction - quark character has changed from udd to uud)
How was the existence of the neutrino hypothesised?
It was found that the energy of particles was lower after beta decay - a particle with 0 charge (to conserve charge) and negligible mass must carry away this excess energy, this particle is the neutrino
What is meant by beta minus decay?
When a neutron turns into a proton, the atom releases an electron and an anti-electron neutrino
What is an alpha particle?
A particle containing 2 protons and 2 neutrons, the same as a helium nucleus
What is an antiparticle?
For each particle there is an antiparticle with the same rest energy and mass, but all other properties are opposite of its respective particle
What is the name of the antiparticle of an electron?
Positron
What is the antiparticle of a pion with zero charge (pi^0)?
(pi^0), it’s its own antiparticle
When does annihilation occur?
When a particle and antiparticle meet
What is annihilation?
When a particle and an antiparticle meet, the mass of the particle and the antiparticle is converted back to energy in the form of 2 gamma ray photons which go in opposite directions to conserve momentum
What is pair production?
A gamma ray photon is converted into a particle-antiparticle pair
What are the 4 fundamental forces?
Gravity,
Electromagnetic,
Weak nuclear,
Strong nuclear
What is the exchange particle of the electromagnetic force?
The virtual photon
What types of particles are affected by the strong nuclear force?
Hadrons
What is the exchange particle of the weak nuclear force?
The W boson (+ or -)
What does the electromagnetic force act on?
Charged objects
When does weak nuclear interaction occur?
When quark character changes - it affects all types of particles
Which properties must be conserved in particle interactions?
Energy,
Charge,
Baryon number,
Lepton number,
Momentum,
Strangeness (only for strong interactions)
What is a hadron?
A class of subatomic particle that experiences the strong nuclear interaction - they’re made up of 2 or more quarks held together by the strong nuclear force - Both baryons and mesons are hadrons
What are the classes of Hadrons?
Baryons (3 quarks),
Mesons (1 quark, 1 antiquark)
What are the 2 classes of Mesons?
Pions,
Kaons
What is the exchange particles of the strong nuclear force?
Gluons and Pions
What particle does a Kaon decay into?
A Pion
What are some examples of Baryons?
A proton - uud,
A neutron - udd
