Particles Flashcards
Specific Charge
Charge to mass ratio.
no. protons * e / no. nucleons * proton rest mass
letter associated with nucleon number & proton number?
nucleon number - A
proton number - z
what is an isotope?
an element with the same number of protons but a different number of neutrons.
State 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.
Describe the range of the strong force?
● Repulsive up to 0.5fm
● Attractive from 0.5-3fm
● Negligible past 3fm
How do nuclei with too many neutrons decay?
Beta minus decay in which a neutron decays to a
proton by the weak interaction emitting an electron and antineutrino.
How was the existence of the neutrino
hypothesised?
The energy of particles after beta decay was lower
than before, a particle with 0 charge (to conserve
charge) and negligible mass must carry away this
excess energy, this particle is the neutrino.
What is an alpha particle?
A particle contains two protons and two 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 the opposite of its respective particle.
What is the antiparticle of π0 (pion with 0
charge) ?
π0, its antiparticle is itself
What occurs when a particle and
antiparticle meet?
Annihilation:
The mass of the particle and antiparticle is converted back to
energy in the form of 2 gamma ray photons which go in
opposite directions to conserve momentum.
2(hf) = 2mc^2 + 2(1/2mv^2)
What is pair production?
A gamma ray photon is converted into a
particle-antiparticle pair.
hf = 2mc^2 + 2(1/2mv^2)
What is the minimum energy of a photon
required to make a proton-antiproton
pair?
2 x proton rest energy
Name the 4 fundamental forces?
● Gravity
● Electromagnetic
● Weak nuclear
● Strong nuclear
Exchange particles for EM?
Weak nuclear?
Strong nuclear?
EM - Virtual Photon
Weak - W bosons
Strong - Pions
What type of particles are affected by the strong
nuclear force?
Hadrons.
When does weak nuclear interaction occur?
When quark character changes (a quark changes
into another quark), 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?
● Baryons (three quarks)
● Mesons (1 quark, 1 antiquark)
What particle does a kaon decay into? MESONS
A kaon decays into a pion.
What is significant about a proton?
● It is the only stable baryon
● All baryons will eventually decay into protons
What are some example of leptons? (fundamental particles)
● Electron
● Muon
● Neutrino
● (the antiparticles of the above)
What does a muon decay into?
An electron
What is the strangeness value of a
strange quark? When is it conserved?
-1
produced through the
strong interaction and decay through the weak interaction.
