2.0 Particles And Radiation Flashcards
What are the three main constituents of the atom
Nucleus: Proton, Neutron
Shells: Electrons
Mass of an electron in relative units
0.0005
Definition of specific charge
Charge - mass ratio
specific charge = Charge/Mass
What is the nuclide notation
A
X
Z
What does A stand for in nuclide notation
Nucleon number
What does Z stand for in nuclide notation
Proton number
Define Isotope
A variation of an element with the same number of protons but different number of neutrons
Use of isotopes
Carbon 14: Carbon dating of organic matter
What is the strong nuclear force
force holding protons and neutrons together in nucleus, counteracting repulsive electromagnetic force between protons
What is the use of the strong nuclear force
Keeping the nucleus stable
What range does the strong nuclear force act
Attraction up to 3 fm with short range repulsion below 0.5 fm
Why can some nuclei be unstable
imbalance between number of protons and neutrons or if the nucleus is too large, causing excessive repulsive forces or insufficient strong nuclear forces to maintain stability.
What is alpha decay
When a nuclei is too large, it can emit an alpha particle to reduce its size via alpha decay
General equation for alpha decay
A A-4 4
X —–> Y + α
Z A-2 2
What is beta decay
When a nuclei is proton or neutron rich, it converts one to the other via beta decay
General equation for beta decay
n/p —-> p/n + e⁻/e⁺ + ̅νₑ/νₑ
What prompted the discovery of the neutrino
The apparent loss of energy and momentum in beta decay, breaking conservation laws, indicating another particle
Define rest energy
The energy equivalent to a stationary particles mass
What is pair production
When a high energy photon converts into a particle-antiparticle pair
Energy in pair production
Photon must have energy of at least combined rest energy of particle-antiparticle pair
What is annihilation
When a particle and its antiparticle collide, converting into a pair of photons
Energy in annihilation
Energy split evenly between photons. So each must have minimum energy of rest energy of particles
What is an antiparticle
Every particle has an antiparticle, with equal mass and rest energy but opposing charge
What is the antiparticle of an electron
Positron
What is the antiparticle of a proton
antiproton
What is the antiparticle of a neutron
antineutron
What is the photon model of electromagnetic radiation
Electromagnetic radiation theorized as small packets of energy called photons
Relationship between frequency and energy of a photon
Frequency is directly proportional to photon energy
Relationship between wavelength and energy of a photon
Wavelength is inversely proportional to photon energy
Momentum in annihilation
photon travel opposing directions to conserve momentum
What are the four fundamental interactions
- Strong nuclear
- Weak nuclear
- Electromagnetic
- Gravitational
What is the exchange particle of the strong nuclear interaction
The gluon or the pion
What is the exchange particle of the weak nuclear interaction
The boson. W⁺, W⁻, Z⁰
What is the exchange particle of the electromagnetic interaction
The virtual photon
What is the exchange particle of the gravitational interaction
The graviton
What is the purpose of the exchange particle
To act as a transfer for conserved properties, to allow forces to act over distances
Particles in strong nuclear interaction
Hadrons
Particles in weak nuclear interaction
Hadron decay, Hadrons and leptons
Particles in electromagnetic force
Charged particles
Examples of the strong nuclear interaction
Force within the nucleus, pion production, alpha decay
Examples of the weak nuclear interaction
beta decay, electron capture, electron-proton collision
What is electron capture?
a proton in the nucleus captures an orbiting electron, converting into a neutron and emitting a neutrino.
What happens in an electron-proton collision?
An electron collides with a proton, producing a neutron and a neutrino.
What is a Feynman diagram?
A diagram that shows the process of an interaction, with time on the y axis and distance on the x axis
What are the 2 main classifications of particle
Hadrons and Leptons
What defines a hadron
They are subject to the strong interaction and are made up of quarks
What are the classes of hadrons
Baryons and Mesons
Composition of baryons or antibaryons
Three quarks or antiquarks
Examples of baryons
Neutron, Proton, Sigma particle
What is the only stable baryon
The proton
What is baryon number
A quantum number that must be conserved
Composition of mesons
A quark - antiquark pair
Examples of mesons
Pion and Kaon
What defines a lepton
Fundamental particles that aren’t subject to the strong nuclear force
Examples of leptons
electron, muon, taon, neutrino
What is lepton number
A quantum number that must be conserved
What is the proton antiparticle
the antiproton
What is the neutron antiparticle
the antineutron
What is the electron antiparticle
the positron
What is the muon antiparticle
the antimuon
What is the neutrino antiparticle
the antineutrino
The decay of a muon
Also called a heavy electron. decay into an electron
What is a strange particle
A particle containing a strange particle
How are strange particles produced
In pairs via the strong interaction
How do strange particles decay
Via the weak interaction
How is strangeness conserved
Conserved in the strong interaction only
How does strangeness change in the weak interaction
Can change by +1, -1, 0
What does particle physics rely on
A collaborative efforts of large teams of scientists and engineers to validate new knowledge
What are the three required quarks
Up, Down and Strange
Properties of the up quark
Charge: +2/3, Baryon number: +1/3, Strangeness: 0
Properties of the down quark
Charge: -1/3, Baryon number: +1/3, Strangeness: 0
Properties of the strange quark
Charge: -1/3, Baryon number: +1/3, Strangeness: -1
Quark structure of a proton
uud
Quark structure of a neutron
udd
Quark structure of a Kaon⁺
us̄
Quark structure of a Kaon⁻
ūs
Quark structure of a Kaon⁰
d̄s or ds̄
Quark structure of a Pion⁺
ud̄
Quark structure of a Pion⁻
ūd
Quark structure of a Pion⁰
uū or dd̄
Beta⁻ decay in form of quark change
d –> u + e⁻ + ve
Beta⁺ decay in form of quark change
u –> d + e⁺ + ν̄e
What properties are conserved
Charge, Energy and Momentum, Baryon number, Lepton number, Strangeness
Define threshold frequency
The minimum frequency required for emission of photoelectrons in the photoelectric effect
The photon explanation of threshold
frequency
Photoelectrons require a certain energy to be released from a surface. Each incident photon interacts with one electron so must have above that required energy, resulting in a minimum frequency of the photon
Define work function
The minimum energy required to remove an electron from a material
Define stopping potential
The minimum negative potential difference required to stop the flow of photoelectrons
released from the surface of a metal
Define ionisation
The process where an atom becomes an ion by removing or adding an electron
Define excitation
When an atomic electron gains a specific amount of energy that it rises energy levels
Process in a fluorescent tube
A flow of electrons cause collisions, and thus excitation of mercury atoms, raising eelectrons up energy levels. When they de-exite, they release UV radiation. UV excites a fluorescent coating, releasing visible light when returning to ground state.
The electron volt
The energy equal to the work done on one electron when accelerating it through a pd of one volt
What are line spectra
emission and absorption spectra of gasses
How do line spectra occur
from the absorption or emission of specific wavelengths in atoms due to discrete energy levels, causing lines corresponding to these levels
theories due to electron diffraction
suggestion that particles possess wave properties
theories due to the photoelectric effect
suggestion that electromagnetic waves
have a particulate nature
What is the De Broglie wavelength
The apparent wavelength of a particle and is inversely proportional to its momentum
Why does less diffraction occur when the momentum of the particle is greater
A greater momentum results in a lower wavelength. lower wavelength is less equal to slit difference and thus less diffraction occurs
How does knowledge and understanding of the nature of matter changes over time
Changes due to experimental evidence cause advances
How must changes be validated
Via peer review and over the scientific community
