Topic 8 Flashcards
What is nucleon number
The sum of the number of protons and neutrons in the nucleus
What is atomic number
The total number of protons in the nucleus
Outline Rutherford’s alpha scattering experiment
High speed alpha particles were fired at a very thin sheet of gold foil. The deflections of the particles were measured and conclusions were drawn
What was observed in the Alpha scattering experiment
- Most of the alpha particles passed straight through the gold atoms.
- Some of them were deflected
- A few of them were deflected backwards
What is thermionic emission
Thermionic emission is the release of electrons due to heating
Why are electrons released from a heated filament
As the filament heats up, free electrons inside the metal gain kinetic energy. When the surface electrons gain sufficient energy, they are released from the surface
What will happen to a beam of electrons if it is passed through a potential difference
The beam of electrons will be accelerated since work is done by the potential difference
How do you calculate the energy transferred to an electron, when it is accelerated across a potential difference
Energy = Charge x Potential difference Energy = eV
What happens when a beam of electrons is directed into a magnetic field
The electron beam will be deflected, since magnetic fields apply forces on moving charges
What is the magnitude of the force experienced by a moving electron in a magnetic field
Force = Magnetic Flux Density x Charge x Velocity F = Bqv
If the electrons are moving perpendicular to the field lines, which direction will the magnetic force act
The fore will act perpendicular to both the electron and field directions
Describe the shape of the path of a beam, of electrons passing through a magnetic field
The beam will produce a circular path since the magnetic force always acts perpendicular to the electrons’ motion. This means it acts as a centripetal force and produces a circular path
What is a cyclotron
A cyclotron is a particle accelerator that uses magnetic fields to accelerate particles in circular paths. This allows higher speeds to be reached, without the limitation of the accelerator’s length
Describe the basic composition of a cyclotron
Cyclotrons consist of two D-shaped paths which are seperated by a small gap. An alternating potential difference is applied across the gap
How does a cyclotron work
An electron beam is passed into the cyclotron, where it is deflected into a circular path by a perpendicular magnetic field. When the beam reaches the gap, it is accelerated by a potential difference. This increases the speed of the beam, causing the radius of the path to increase. This process repeats every half circle.
State the equation used to calculate the circular radius of an electron beam deflected in a magnetic field
Radius = (mass x velocity) / (magnetic flux density, B, x charge)
What two equations must you combine to derive the radius equation
- Centripetal Force = (mv^2)/r
- Magnetic Force = Bqv
Centripetal force = Magnetic force
State the mass energy equation
E = mc^2
What is 1 eV in joules
1 eV = 1.6x10^-19 J
In the quark-lepton model, what are the four main categories of particles
- Baryons
- Mesons
- Leptons
- Photons
Describe the quark compostion of a baryon
Baryons are made up of three quarks
Describe the quark composition of a meson
Mesons are made up of a quark and antiquark pair
Which category of particles are classed as fundamental particles
Leptons
Give two examples of leptons
- Electrons
2. Neutrinos
What category of particles do pions belong in
Mesons
Give two examples of baryons
- Protons
2. Neutrons
What did the symmetry of the quark-lepton model predict the existance of
The top quark
What is an antiparticle
An antiparticle is one that has the same mass but opposite charge and conservation numbers to its corresponding particle
What is the antiparticle of a proton
An antiproton
What is the antiparticle of an electron
A positron
Name four things that are always conserved in a particle interaction
- Mass/Energy
- Baryon number
- Lepton Number
- Charge
Describe the conservation of lepton number
The lepton number for each specific type of lepton must be the same before and after an interaction
