Particles Flashcards
What is the mass (kg) of a proton or neutron?
1.67x10⁻²⁷
What is the Charge (C) of a proton and electron?
Proton: +1.6x10⁻¹⁹
Electron: -1.6x10⁻¹⁹
What is specific charge?
Specific charge is the charge per unit of mass of a particle.
How do you calculate specific charge?
specific charge(Ckg⁻¹) = Charge(C) / Mass(kg)
What happens to the Wavespeed, Wavelength and Energy of EM waves as their frequency increases?
Wavespeed stays the same.
Wavelength decreases.
Energy increases.
Name all parts of the EM spectrum from low-high frequency.
Radiowaves.
Microwaves.
Infrared.
Visible Light.
Ultraviolet.
X-ray.
Gamma.
What symbol is used to represent the speed of light?
c
What symbol is used to represent Planck’s Constant?
h
What are photons?
Small packets of energy formed by quantising light.
How do you calculate the energy of a photon?
E = hf
Or
E = hc / λ
What is minimal energy?
Minimal energy is used instead of mass to describe quantum particles.
How do you calculate the minimum energy of a particle?
E = mc²
What equation links Energy(E), Charge(Q) and Voltage(V)?
E = QV
Energy = Charge x Voltage
Why can’t anything travel faster than light?
As particles approach “c” they gain mass. At “c” the mass becomes infinite. It is impossible to accelerate beyond light as an infinite force would be needed.
What is minimum energy measured in?
Electron volts (eV)
How many Joules (J) in one electron volt?
1.6x10⁻¹⁹J
Same as the charge of an electron or proton.
What is the strong force?
A short range force that works on quarks. It keeps the nucleus stable.
What is the equation for Beta minus decay?
Neutron —> proton + electron + antineutrino
What is the equation for Beta plus decay?
Proton —> neutron + positron + neutrino
What are the characteristics of antimatter?
For every particle there is a corresponding antiparticle.
Antiparticles have the same mass but opposite properties.
What happens when a particle and antiparticle collide?
ANNIHILATION
Why are two photons propelled in opposite directions when annihilation occurs?
Because both momentum and energy must be conserved.
What is pair production?
When high energy photons produce a particle and antiparticle. (The particles are propelled in opposite directions)
List the fundamental forces from strongest-weakest.
Strong Force, Electromagnetic Force, Weak Force, Gravity
List the fundamental forces from longest-shortest range.
Electromagnetic and Gravity, Strong force, Weak force
What is the range of the strong force?
3fm
What is the range of the weak force?
0.001fm
What is the range of the Electromagnetic force?
Infinite
What is the range of the Gravitational force?
Infinite
What is the relative strength of the strong force?
1
What is the relative strength of the weak force?
1x10⁻⁶
What is the relative strength of the Electromagnetic force?
1x10⁻²
What is the relative strength of the gravitational force?
1x10⁻³⁸
What are the exchange particles of the strong force?
Gluons (g) and pions (π)
What is the exchange particle of the weak force?
W and Z boson (W⁺, W⁻, Z⁰)
What is the exchange particle of the Electromagnetic force?
Virtual photon (γ)
What is the exchange particle of the gravitational force?
Graviton
Why does the weak force have such a short range?
W bosons are very large and have a larger mass which results in a shorter range.
What determines the range of a fundamental force?
The mass of its exchange particle.
Why does the Electromagnetic force have an infinite range?
Photons have a mass of 0 and since range is determined by mass the range is infinite.
Why does the strong force have a short range?
Gluons interact with each-other.
What are the two types of lepton?
Electron and neutrino
What are the 3 types of charged leptons?
Electron (e), Muon (μ), Tau (τ)
What are the 3 types of neutrino (leptons)?
Electron neutrino (Ve), Muon neutrino (Vμ), Tau neutrino (Vτ)
What are the 6 flavours of quark?
Up, Down, Strange, Charm, Top, Bottom
What is the charge and strangeness of an Up quark?
Charge = 2/3, Strangeness = 0
What is the charge and strangeness of a Down quark?
Charge = -1/3, Strangeness = 0
What is the charge and strangeness of a Strange quark?
Charge = -1/3, Strangeness = -1
What is the charge and strangeness of an Anti-Up quark?
Charge = -2/3, Strangeness = 0
What is the charge and strangeness of an Anti-Down quark?
Charge = 1/3, Strangeness = 0
What is the charge and strangeness of an Anti-Strange quark?
Charge = 1/3, Strangeness = +1
What quarks make up a proton?
2 up, 1 down
What quarks make up a neutron?
2 down, 1 up
What quarks make up an Anti-proton?
2 anti-up, 1 anti-down
What quarks make up an anti-neutron?
2 anti-down, 1 anti-up
What are Baryons made up of?
3 quarks
What are mesons made up of?
Quark and anti-quark
What are the two types of mesons?
Kaon (K⁺, K⁰, K⁻) - strange,
Pion (π⁺, π⁰, π⁻) - not strange
What forces affect quarks?
Weak force, EM force, Strong
What forces affect charged leptons?
Weak force, EM force
What forces affect uncharged leptons?
Weak force
Describe the effect of the strong force as nucleons separate more and more.
When the nucleons are less than 0.5fm the strong force has a repulsive effect. This repulsive effect causes the nucleons to separate until 0.5fm and then the strong force starts to have an attractive effect upon the nucleons. However, if the nucleons are separated by more than 1.5fm the effect of the strong force rapidly declines until 3fm when it stops having an effect on the nucleons.
What is the mass(kg) of an electron?
9.11x10⁻³¹
Describe the Feynman diagram for β⁻ decay.
Neutron. Produces proton left, β⁻ up right, anti-Ve lower right. W⁻
Describe the Feynman diagram for β⁺ decay.
Proton. Produces neutron up left, β⁺ up right, Ve lower right. W⁺
Describe the Feynman diagram for electron capture.
Proton and electron. Produces neutron up left, Ve up right. W⁺
Describe the Feynman diagram for proton-antineutrino.
Proton and anti-Ve. Produces neutron up left, positron up right. W⁺
Describe the Feynman diagram for Neutron-neutrino.
Neutron and Neutrino. Produces proton up left and electron up right. W⁻
Describe the Feynman diagram for Proton-Proton.
Proton and proton. Produces proton up left, proton up right. γ
Describe the Feynman diagram for Electron-Electron.
Electron and electron. Produces electron up left, electron up right. γ
When is strangeness conserved?
In strong and EM interactions.
What is the minimum required energy in pair production determined by?
The total rest mass of the particles being produced.
What happens if a photon exceeds the minimum required energy for the pair production of an electron and positron?
The excess energy is transferred to the particles kinetic energy store. They get propelled faster.
What is the photoelectric effect?
When the energy from light (photons) hitting a metal surface is great enough to cause electrons to be released from the metal surface.
How does increasing light intensity affect the number of electrons released (photoelectric effect)?
The intensity of light does NOT affect the number of electrons released.
How does the frequency of light affect the electrons emitted (photoelectric effect)?
The higher the frequency the higher the energy of individual photons.
There is a minimum required energy the photons must have for photoelectrons to be emitted from the metal known as the work function.
The threshold frequency corresponds to this energy.
What is the name for the minimum energy of a photon to cause an atom to emit a photo-electron?
The work function (Φ)
How do you calculate the work function (photoelectric effect)?
Work function = Planck’s constant x Threshold frequency
Φ = h x f(min)
How do you calculate the excess kinetic energy in an electron (photoelectric effect)?
Eₖ = hf - Φ
What is kinetic energy also equal to?
½mv²
How are electrons organised in an atom?
Into quantised energy levels (shells)
In an energy level diagram what do the negative energy labels mean?
They mark how much energy would be needed for the electron to be removed from the atom.
For example if n = 1 was labelled, -13.59 E/eV, this would mean if the electron gained +13.59 it could escape the atom
What is ionisation?
The process of an atom losing an electron causing the atom to become a positively charged ion.
What is ionisation energy?
The energy required by for an electron to be removed from an atom from the ground state
Why is ionising radiation harmful?
It causes cell structure such as DNA to become ionised. This prevents cells from functioning normally, so they mutate or die.
What must happen for an electron to be excited to a higher energy level?
It must have the exact difference in energy required to move to a higher energy level. This is because energy levels are quantised (discrete) and require the exact energy needed.
How can electrons in an atom gain energy?
Interacting with another electron.
Interacting with a photon.
What is the difference between excitation and ionisation?
Excitation is when an electron moves to a higher energy level.
Ionisation is when an electron gains enough energy to escape the atom.
How could an electron de-excite or relax?
By losing energy, caused by emitting a photon of energy equal to the difference between energy levels.
How do fluorescent tubes work?
An electric current is passed through the tube causing high energy electrons to be emitted from a cathode.
This cause electrons in mercury to be excited to a higher energy level.
This is unstable for mercury so the electrons de-excite and release photons of energy equal to the difference in energy levels.
The photons produce a UV light (EM wave) that then interacts with the phosphor coating.
The electrons in the phosphor are excited.
This is unstable so the they de-excite and release the visible light that we see.
Describe what an emission spectra is?
Passing an electric current through hydrogen (g) and then passing the light produced (from the electrons de-exciting) through a diffraction grating will produce a pattern of coloured bands.
Wavelengths of light are equal to that of energy level difference because of the photons emitted.
What is an absorption spectra?
When white light of all wavelengths passes through a gas, the gas will absorb the wavelengths of light that correspond with its discrete energy levels.
This results in the image having a spectrum of light with lines of emptiness in some places.
How do you calculate the De Broglie wavelength of a particle?
λ = h / mv
λ = h / p
p is momentum
What meson decays and why?
Kaons decay because they are large and unstable.
What do kaons decay into?
Pions as they are light and more stable.
K⁰ —> π⁺ + π⁻
How are strange particles produced and how do they decay?
Strange particles are always produced through the strong interaction (gluon)
They decay through the weak interaction (W and Z bosons)
How are strange particles produced and how do they decay?
They are produced through the strong interaction (gluon)
They decay through the weak interaction (W and Z bosons)
What are the most common forms of decay for leptons?
Muon —> Electron
Anti muon —> Positron
Why do muons decay into electrons?
Muons are larger and more unstable than electrons and so decay through a weak interaction.
When electrons and protons interact with each other what force facilitates it?
Weak force, as they will undergo decay.
What boson mediates electron capture?
W⁺
What boson mediates electron-proton collision?
W⁻
What directions does the exchange particle travel in electron-proton collision?
W⁻ travels right to left.
What direction does the exchange particle travel in electron capture?
W⁺ travels left to right
What is the work function?
The minimum energy required by an electron to escape from a metal surface
