Nuclear and particle physics Flashcards
radius of an atom
1 x 10^-10
radius of a nucleus
1 x 10^-15
definition of an isotope
- have the same number of protons but a different number of neutrons
How are Em radiation released
- electrons are arranged at different distances from the nucleus (different energy levels or orbits)
- Change in orbit when they absorb em radiation (increase in energy)
- em released when returns to lower orbit
what is Ionsisation
if the electromagnetic radiation has sufficient energy, it can cause the electron to escape from the atom completely.
this is called ionisation
, the atom is now charged.
what did rutherford experiment and what did he observe
Experiment:
1. Placing an alpha emitter which fires in straight lines (high speed)
2. Placing a line of gold foil.
3. GM tubes placed around to detect the alpha particles.
Observations:
1. Most alpha particles went straight through the gold.
2. Some alpha particles were deflected by the foil.
3. A few were bounced back.
what was their conclusions?
- mostly empty space (orbiting electrons)
- positively charged nucleus (most mass)
Time line of solving the atom
- 450 bc democratis atoms
- Dalton 1803 atoms are the building blocks of everything
- Thompson 1897 electrons
and the plum pudding model - Rutherford 1911 nucleus +orbit
+ empty space
what are ions
atoms have a neutral charge as they have the same number of protons and electrons
ionisation occured if they lose or gain an electron
they become charged
what is a nucleon number
the sum of the number of protons and neutrons in the nucleus
what is the atomic number
the total number of protons in the nucleus
what is thermionic emission
it is the release of electros due to heating
explain why electrons are 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 passed through a potential difference and how?
what ?the beam of electrons will accelerate since work is done by the potential difference
How? A p.d. creates an electric field between two points, typically the cathode (negative) and anode (positive).
Electrons, being negatively charged, experience a force due to the electric field
F=qE
where q = -e
Newtons second law F=ma. so if there is a force there must be an acceleration
what is the equation to calculate the energy transferred to an electron when accelerated across a pd
energy = charge x pd
Ke = eV
What is in a cathode ray tube and what are there functions
Cathode: Emits electrons when heated (thermionic emission).
Anode: Positively charged to accelerate the electrons.
Vacuum Tube: Reduces collisions with air molecules, ensuring free movement of electrons.
Fluorescent Screen: Emits light when struck by high-speed electrons.
how does a cathode ray tube work
Heating the cathode causes electrons to be released via thermionic emission.
A high potential difference between the cathode and anode accelerates the electrons.
The electron beam strikes the fluorescent screen, creating a visible spot of light.
How are electron beams deflected in a cathode ray tube?
Plates inside the CRT create a uniform electric field when a p.d. is applied.
The force on electrons
F= qE (field strength) causes deflection perpindicular to the direction
Magnetic fields apply a force on moving electrons via the lorentz force
F = Bev x sin theta
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 (T) x Charge (c) x Velocity (ms^-1)
F=Bev
if the electrons are moving perpindicular to the field lines which direction will the magnetic force act
the force 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 perpindicular 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 accelerators length
describe the basic composition of a cyclotron
cyclotrons consist of two D shaped paths which are seperated by a small gap. an alternating pd 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 an field. This increases the speed of the beam, causing the radius the path to increase. This process repeats every half cycle, building the velocity..
What is a linear accelerator (LINAC)?
A LINAC accelerates charged particles in a straight line.
It uses a series of drift tubes and oscillating electric fields.
Applications include cancer treatment, particle physics, and generating X-rays.
How does a LINAC work?
Charged particles are emitted from a source.
Alternating electric fields between drift tubes accelerate particles.
Drift tube lengths increase to match the particles’ increasing speed.
Particles emerge at high energy for use in experiments or treatments
What is the basic composition of a LINAC (Linear Accelerator)?
Source of Charged Particles: Emits particles (e.g., electrons, protons).
Drift Tubes: Hollow, cylindrical tubes where particles are shielded from electric fields.
Oscillating Electric Fields: Alternating electric fields between the drift tubes accelerate particles.
Power Supply: Provides high-frequency alternating voltage.
Beam Exit: Directs the accelerated particle beam to its target.
What is a bubble chamber?
A bubble chamber detects charged particles.
It is filled with a superheated liquid (e.g., liquid hydrogen).
Particles leave trails of bubbles as they pass through the liquid.
How does a bubble chamber work?
A charged particle passes through the superheated liquid.
The particle ionizes the liquid along its path.
Bubbles form along the ionization trail, making the path visible.
A magnetic field is often applied to curve the paths, revealing momentum and charge.
What is the basic composition of a bubble chamber?
Superheated Liquid: Usually hydrogen, maintained just below its boiling point.
Magnetic Field: Curves particle paths to determine charge and momentum.
Chamber Walls: Transparent to allow observation and photography of bubble trails.
Pressure Control System: Quickly decreases pressure to create superheating.
Camera System: Captures images of particle tracks for analysis.
What is a cloud chamber?
A cloud chamber visualizes charged particle tracks.
It contains a supersaturated vapor (e.g., alcohol).
Tracks appear as condensation along ionized paths.
How does a cloud chamber work?
Charged particles ionize the vapor in the chamber.
The ionized vapor condenses, forming visible tracks.
Track curvature in a magnetic field reveals particle properties (e.g., charge and momentum).
What is the basic composition of a cloud chamber?
Chamber Body: Enclosed area containing supersaturated vapor, often alcohol.
Cold Plate: Maintains a temperature gradient to create supersaturation.
Source of Charged Particles: Emits particles that ionize the vapor.
Light Source: Illuminates the chamber to make tracks visible.
Viewing Window or Camera: Allows observation or recording of particle tracks.
What is a GM tube?
A GM tube detects ionizing radiation (alpha, beta, gamma).
It consists of a gas-filled chamber, electrodes, and a thin window.
It produces electrical pulses when radiation ionizes the gas.
How does a GM tube work?
Ionizing radiation enters the tube, ionizing the gas inside.
Free electrons are attracted to the positive electrode, creating a cascade of ions.
The ionization causes an electrical pulse.
The pulses are counted to measure radiation intensity.
What is the basic composition of a GM Tube (Geiger-Müller Tube)?
Metal or Glass Cylinder: Acts as the outer casing and contains the gas.
Inert Gas: Usually argon or helium, with a trace of halogen for quenching.
Anode Wire: A thin, central wire that collects electrons during ionization.
Cathode Shell: The outer conductive surface, held at a negative voltage.
Thin Window: Allows low-energy particles (e.g., alpha radiation) to enter.
Electronics Circuit: Amplifies and counts the electrical pulses from ionizing events.
state the equation used to calculate the circular radius of an electron beam deflected in a magnetic field
Radius = mass x velocity
————————
flux denisty x charge
r = mv/bq
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 MeV
it is 1 Mega electron volt
which you can calculate what it is in in joules by doing 1.6x10^19 x 10^6
what is 1 U of mass and what is it = to
it is 1 unified atomic mass unit
and it = 1.66 x 10^-27
what does the equation e = mc^2 mean
it means mass can be converted into energy, and energy can be converted to mass
when a small amount of mass is converted, a large amount of energy is released due to the c^2 factor
in the quark-lepton model, what are the four main categories of particles?
- Baryons > Hadrons
- Mesons> Hadrons
- Leptons
- Photons
what is a Hadron
any particle made of quarks
what are the 6 types of quark
up U
top t
Down d
Bottem b
Strange s
Charm c
what is the quark composition of a Baryon
3 Quarks
what is the quark composition of Mesons
2 quarks or a quark and anti quark
give me 6 examples of Baryons
protons
neutrons
ant protons
anti neutrons
lamba particle
sigma particle
what is the quark construction for Protons and for anti proton
2u 1d
_ _
2u 1d
what is the quark construction for neutrons and for anti neutrons
2d 1u
_ _
2d 1u
whats the quark construction for a lambda particle
1u 1d 1s
what are 2 types of mesons
pions
kaons
what is the quarks construction of a pion and the symbol
Pi symbol for pions
_
pi + = u d
_
pi - = u d
_ _
pi 0 = uu or dd
what is the quark construction of a kaon and its symbol
_
K + = u s
_ _
K 0 = d s or s d
_
K- = s u
what is a lepton?
leptons are fundamental particles
what are the 3 versions of lepton
electron e
muon mu (u)
tau T( squiggly t)
what is there charge
-1
what are the anti versions of the letpons
electron = positron
muon = anti muon
tau = anti tau
whats the relationship between these fundamental particles
there mass increases from electron to muon to tau
what is a neutrino lepton
it is a neutral particle belonging to the lepton family
what are the 3 types of neutrino lepton and there anti pair
electron neutrino
- electron anti neutrino
_
Ve and Ve
muon neutrino
- muon anti neutrino
_
Vu and Vu
Tau neutrino
- Tau anti neutrino
_
Vt and Vt
all have a charge of 0
what is the definition of an anti particle
an anti particle is one that has the same mass but oppositly charged and conservation numbers to its corresponding particle
name four things that are always conserved in a particle interaction
- mass/energy
- Baryon Number
- Lepton number
- charge
Desvribe the conservation of a lepton number
the lepton number for each specific type of lepton ,must be the same before and after an interaction
what was a consequence of einstiens theory of relativity
the mass of an object increases with its velocity relative to the observer.
matter can be converted to energy and energy can be converted to matter
Define the rest mas
the rest mass of an object is its mas when the object is stationary
what is the definition for rest energy
the rest energy of a body is the energy it has by virtue of the mass alone. therefore the mass can be regarded as a form of energy. The rest energy of a body is in addition to any ke or pe it might have
what is the equation for rest energy
if the mass of a body is m0 , when it is at rest its energy is
Rest energy
E0 =m0 x c^2
define pair production
pair production is the formation of two electrons (one negative and the other positive (positron), from a pulse of electro magnetic energy travelling in the area of a atomic nucleus.
Pair production is a direct conversion of radiant energy to matter
what m
what must be true for pair production to occur
the em energy, in form of a photon, must be equal to at least equivalent to the mass of 2 electrons, the mass of a single electron = 0.51MeV so therefore energy of photon must be at least 1.02 MeV
