Topic 8: Nuclear And Particle Physics Flashcards
What are the 3 constituents an atom is formed of?
An atom is formed of protons, neutrons and electrons.
What is a nucleon?
At the centre of the atom is a nucleus formed of protons and neutrons; these are nucleons.
Not electrons as they orbit the nucleus in shells.
What is the proton and nucleon number?
The proton number is the number of protons in an atom. (Bottom number)
Nucleon number is the number of nucleons (protons and neutrons) in an atom. (Top number)
What does the Rutherford’s gold foil experiment consist of?
Rutherford’s gold foil experiment consists of;
- Alpha particle source and gold foil (malleable and thinnest metal)
-in excavated chamber
-covered in fluorescent coating (to see where particles hit in the chamber)
What were the observations and conclusion of Rutherford’s gold foil experiment?
1) Most alpha particles passed straight through — Atom is mainly empty space
2) Some alpha particles deflected at slight angle — centre of atom is positively charged as positive alpha was deflected from the centre.
3) Very few deflected at <90° — centre of atom was very small but very dense as very small amount of particles deflected at large angle and could deflect fast moving particles
Results showed the atom has a small, dense, positively charged nucleus in the centre.
What is thermionic emissions?
Thermionic emission is when a metal is heated via a current until the free electrons gain enough energy to leave the surface.
What are the properties that must always be conserved during particle interactions?
During particle interaction; following properties must be conserved
- Charge
- Momentum
- Energy
What is a bubble chamber?
A bubble chamber is a t tank filled with superheated liquid hydrogen which forms bubbles around any ionised particles created as a result of movement of charged particles.
What is the purpose of a bubble chamber?
Using a bubble chamber, you can observe the path taken by moving, charged particles.
What can you tell from a track in a bubble chamber stopping, changing direction or coming from nothing?
Track suddenly stops - particles collided
Track changes direction - Particles have collided
Tracks come from nothing - particles created from uncharged particle (photon)
What is de Broglie’s relation + formula?
de Broglie’s relation shows that a particle’s wavelength and momentum are inversely proportional
λ = h/p
λ - de Broglie’s wavelength
h - Planck constant
p - momentum of particle
What does de Broglie’s relation tell you?
The smaller the de Broglie wavelength, the higher energy/momentum of the particle required.
Why are high energies needed to investigate structure of nucleons?
Nucleons are incredibly small
- need to use very small wavelengths
- so particles have extremely high energies
What did the theory of special relativity prove?
Mass and energy are interchangeable
ΔE = Δmc²
What is pair production?
Pair production is when a photon is coverted into an equal amount of matter and antimatter.
What are the conditions for pair production to occur?
For pair production to occur;
- initial photon has an energy greater than the total rest energy of both particles
- excess energy converted into kinetic energy for particles
What is annihilation?
Annihilation is when a particle and its corresponding particle collide.
What are the results of annihilation?
Their masses are converted to energy and released in the form of 2 photons moving in opposite directions in order to conserve momentum.
What is an electronvolt?
An electron-volt (eV) is a unit of energy used to represent small energies.
It is equal to the kinetic energy of an electron accelerated across a p.d of 1V.
1.6 x 10⁻¹⁹ J
Covert MeV/GeV to J
MeV = 1eV x 10⁶ = 1.6 x 10⁻¹³
GeV = 1eV x 10⁹ = 16.x10⁻¹⁰
What are the 3 classifications of particles?
Hadrons, leptons or photons
What fundamental particle?
Fundamental particles are particles that can’t be broken down further. Usually leptons
What are are all hadrons formed of and what are the 2 different types?
Hadrons are formed of quarks and experience strong nuclear force
The 2 types are
- Baryons
- Mesons
What are baryons and mesons made up of?
Baryons are formed of 3 quarks/antiquarks
Mesons are formed of a quark and anti-quark
What are anti-particles?
For every type of particle it has a corresponding anti-particle.
Anti-particles have same rest energy and mass but all other properties are opposite.
How to determine if a particle interaction is possible?
All the following properties must be conserved;
- Charge
- Baryon number
- Lepton number
What are the common baryons?
Protons & neutrons
What are common mesons?
Pion and kaon
What are common leptons?
Electrons
Muon
Neutrino particles
Explain how the cyclotron produces the high-energy proton beam
- There is alternating pd
- p.d accelerates protons between dees
- Magnetic field perpendicular to plane of dees
- Proton path curved by magnetic field, moving in circular motion
- As velocity increases, radius of path in dees increase
- Time for which proton is in a dee remains constant
Explain why electrons need high energies to investigate the structure of a proton.
High energy electrons will have short de broglie wavelength
Wavelength needs to be comparable to proton size
Explain how an electron is accelerated in a linac
- Set of metal drift tubes in a line
- Electrons accelerated by p.d
- Acceleration takes place in gaps between tubes
- Adjacent tubes connected to opposite terminals of power supply
- p.d is alternating so as electron emerges from tube, next tube is positive
- Time spent in each tube must be same so tubes get longer each time
Explain how electrons from the source become a beam of high-energy electrons travelling through a p.d
- p.d creates an electric field
- Electric field does work on electrons, increasing kinetic energy
