Particles Flashcards
What are the main constituents of the atom?
*Proton
*Neutron
*Electron
Define specific charge
Specific charge = charge / mass
Specific charge of a proton?
Charge = 1.6x10^-19
Mass 1.67x10^-27
1.6x10^19/1.67x106-27 = 9.58x10^7
What is the letter associated with proton number?
Z
What is a nucleon?
A constituent of the nucleus : a proton or neutron
What letter represents nucleon number?
A
Which is correct: AXZ or ZXA?
AZX
What is an isotope?
Two elements that have the same amount of protons but a different amount of neutrons
State a use of radioactive isotopes
*Carbon dating - The proportion of carbon-14 in a material can be used to determine its age
*Cancer detection
What is a strong nuclear force?
The fundamental force that keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons
Describe range of strong force
*Repulsive up to 0.5fm
*Attractive from 0.5-3fm
*Negligible past 3fm
What makes a nucleus unstable?
Nuclei that have far too many protons, neutrons or both
How do nuclei with too many nucleons decay?
Alpha decay
How do nuclei with too many neutrons decay?
Beta minus decay (udd to uud)
How is the existence of a neutrino hypothesised?
The energy of particles after beta decay was lower than before, a particle with 0 charge and negligible mass must carry away this excess energy, this particle is a 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 that contains two protons and two neutrons
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
Antiparticle of an electron
Positron
Antiparticle of Pi0
Pi0
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 photos which go in opposite directions to conserve momentum
Pair production definition
A gamma ray photon is converted to a particle-antiparticle pair
Min energy of a photon required to make a proton-antiproton pair
2 x proton rest energy
2 x 9.38.257 = 1876.514 MeV
4 Fundamental forces
*Gravity
*Electromagnetic
*Weak nuclear
*Strong nuclear
The virtual photon is the exchange particle of which force?
The electromagnetic force
What type of particle is affected by the strong force?
Hadrons
What is the exchange particle of the weak nuclear force?
W boson (W- or W+)
What does the electromagnetic force act?
It acts on all charged objects, for example when a positively charged ball repels another positively charged ball
When does weak nuclear interaction occur?
When a quark changes, it affects all types of particles
What property must be conserved in particle interactions?
*Energy
*Charge
*Baryon number
*Lepton number
*Momentum
*Strangeness
What is a hadron
Both baryons and mesons are hadrons, made up of at least 2 quarks and interact via strong nuclear force
Classes of hadrons
*Baryons - qqq
*Mesons - quark antiquark
Pion and kaon are both examples of which class of particles?
Mesons
The pion can be a exchange particle for which force?
Strong nuclear force
What particle does a kaon decay into?
A kaon decays into a pion
Example of baryons
*Proton - uud
*Neutron - ddu
What is significant about a proton?
*The only stable baryon
*All baryons will decay into protons
Examples of leptons
*Muon
*Electron
*Neutrino
Examples of leptons
*Muon
*Electron
*Neutrino
What does a muon decay into?
An electron
What is the strangeness value of a strange quark?
-1
