1. Matter and Radiation Flashcards
What is the strong nuclear force?
Keep the nucleus stable by counteracting electrostatic force of repulsion. They are short ranged, and act within the nucleus.
Exchange particle: Gluon
What is an unstable nuclei?
A nuclei with too many protons, neutrons or both, and the SNF is not strong enough to keep the nucleons stable and will decay.
What is alpha decay?
A helium nucleus is released.
What is Β- decay?
When a neutron turns into a proton and an electron and an anti electron neutrino is released.
n –> p + e- + anti electron neutrino
Exchange particle: W-
Why is there a neutrino in B- Decay?
To obey the law of conservation of energy
What are photons?
They are packets of energy
E = hf
What is annihilation?
When a particle and its corresponding antiparticle collide, resulting in two photons moving in opposite directions to conserve energy and momentum.
What is pair production?
When one photon converted into a particle and antiparticle, where the photon has a greater energy than the rest mass energy of the particles. The excess energy is converted into KE
What are exchange particles?
They carry energy and momentum between the particles experiencing the force.
What is gravitational force?
The attractive force between two objects with masses, and can have large ranges.
Exchange particle: Graviton
What is electromagnetic Force?
The force between to charged objects, and are long ranged.
Exchange particle: Photon
What is the weak force?
Force responsible for decay on charge particles.
Exchange Particle: W Boson
What is a B+ Decay?
When a B+ particle and electron neutrino is released
p –> n + e+ + electron neutrino
W+
What is electron capture?
When an electron is absorbed into a nucleus.
p + e- –> n + electron neutrino
W+
What is electron proton collision?
p + e- –> n + electron neutrino
W-
What are Leptons?
They are fundamental particles and do not experience SNF
What are hadrons?
They can be split into baryons and mesons and experience SNF
Which is the only stable baryon?
Proton, other baryons decay
Baryon Number
Baryon = 1
Anti baryon = -1
Lepton Number
Lepton = 1
Antilepton = -1
What are the different baryons?
Protons and neutrons
What are the different leptons?
Electrons, muons and neutrinos
What are the mesons?
Pions and kaons
Strangeness
Strange particle = -1
Antistrange particle = 1
Must always be conserved in strong interactions
Can differ by 1 in weak interactions
quark combinations of proton and neutron
proton = uud
neutron = udd
What do kaons decay into?
Pions
What do muons decay into?
Electrons
How are strange particles produced and decayed?
Produced by strong interactions in pairs and decay by weak interactions
What is the threshold frequency?
The minimum frequency required for a photon to be absorbed by the electrons so the photoelectrons can be emitted from the surface of a metal.
What is the work function?
A photon is completely absorbed by an electron. This is the minimum energy needed for a photon to emit a photoelectron from the surface of a metal.
What is the stopping potential?
The potential difference needed to apply across the metal surface to stop the photoelectrons with maximum kinetic energy from being released. `
What is the photoelectric equation?
hf = φ + Ek(max)
What happens if the intensity of the light is increased?
If the frequency is above the threshold, more photons are emitted per second.
What is ionisation?
The energy needed to completely remove an electron from its orbital/ atom.
What is excitation?
When an electron moves up energy level by gaining energy
Evidence for discrete energy levels?
The line spectra have distinct lines and are not continuous. Electrons need energy equal to the difference in energy levels to move up energy levels. The electrons releases the same amount of energy when they de-excite.
Electron Duality
Electron diffraction suggests wave properties
Photoelectric effect have particulate nature
De broglie wavelength equation
λ = h/mv
How do fluorescent tube lights work?
The current allows charge to be passed through the tube and collide with the Mg atoms. This excited the electrons in the Mg atom, when they de-excite they release photons in the UV range. The fluorescent coating inside absorbs the photons and and the electrons are excited and de-excite releasing photons of visible light.
Relationship between intensity of light and maximum kinetic energy of electrons
They are independent to each other
Each electron can only absorb one photon
Ek is dependent on frequency of incident radiation
Won’t increase EK but increase the rate of photoelectrons emitted
relationship between photoelectric current and intensity
They are proportional as the rate of photoelectrons emitted have increased therefore current increases
