Particles and Radiation Flashcards
How to calculate specific charge and its unit
Define Specific Charge
Charge ÷ Mass
Ckg¯¹
Charge per kg of a particle
What is an isotope
An atom with the same number of protons but different number of neutrons
In the diagram, what does the 4 represent and the 2 represent
4 is the atomic mass - no. of protons + neutrons
2 is the atomic number - number of protons
What is the strong nuclear force, and its graph
Force that counteracts the electrostatic force of attraction between protons in the nucleaus, keeping the nucleaus together
Has a range of 3-4 fm
Below 0.5 fm, it acts as a repulsive force to stop nucleons being pushed into each other
When is a nucleaus unstable
When it has too many of either protons, neutrons or both causing the SNF to not be enough to keep them stable, therefore these nuclei will decay in order to become stable.
What is alpha decay
Decay of a nucleus when there are too many protons and neutrons
An aplha particle that has 2 protons and 2 neutrons in emitted
What is Beta Minus Decay
Decay of a nucleus that has too many neutrons
The neutron turns into a proton which stays in the nucleus
This causes an electron to be emitted as a Beta particle with a neutrino
n → p + e- + νe
What is an antiparticle
Has the same rest energy and mass, but all other properties are opposite to its corresponding particle
What is a photon
Packet of electromagnetic energy which transfers energy and has no mass
Equation for photon energy
E = hf = hc/wavelength
h = Planck constant
c = speed of light
f = frequency
What is annihilation
Give an application of it
Where a particle and its corresponding antiparticle collide, as a result their masses are converted into energy. This energy, along with the kinetic energy of the two particles is released in the form of 2 photons moving in opposite directions in order to conserve momentum.
PET scans
What is pair production
Where a photon is converted into an equal amount of matter and antimatter. This can only occur when the photon has an energy greater than the total rest energy of both particles, any excess energy is converted into kinetic energy of the particles.
What is a particles rest energy
Energy of a particle when it is not moving
K.E is 0
What are the 4 particle interactions, their exchange particles, ranges and what they act on
Strong interaction acts on Hadrons
Weak interaction acts on all particles
Electromagnetic Interaction acts on charged particles
Gravity acts on all particles with mass
What is an exchange particle
A particle that carries energy and momentum between the particles experiencing the force and each fundamental force has its own exchange particles.
Intercepting it will stop the reaction from happening
It causes the forces between partcles in a reaction
What are the 4 interactions caused by the weak nuclear force
Beta Minus Decay
Beta Plus Decay
Electron Capture
Electron proton Collision
Electron Capture
p + e − → n + ν(e)
When a nucleus has too many protons, it takes an electron from the atoms inner energy level so it interacts with a proton to produce a neutron and antineutrino
A W^+ Boson is the exchange particle
So the proton loses its positive charge and the electron gains positive charge
Electron - proton Collision
p + e − → n + ν(e)
When an electron and proton collide at a high speed, a W¯ Boson will take negative charge from the electron to the proton, producing a neutron and neutrino
Beta Plus Decay
A proton in a proton rich nucleus decays into a neutron, emitting a W+ Boson
W+ Boson decays into a positron and neutrino
What is a Lepton
Fundamental particle
Not made up of quarks
Interact through all but the Strong Nuclear force
eg. Electron, Muon, Neutrino
What is a Hadron
Any particle made up of quarks
Experiences all 4 interactions
What is a Baryon
Hadron formed of 3 quarks
eg. a Neutron, proton
What is a Meson
Hadron formed of a quark, antiquark pair
eg. A pion, Kaon
What is the only stable Baryon. What does this therefore mean
Proton
All Baryons will eventually decay into a proton
What is Baryon Number
Shows if a particle is a baryon
Baryon = 1
Not a Baryon = 0
Antibaryon = -1
Always conserved
What is Lepton Number
Shows if a particle is a Lepton
Lepton = 1
Not a Lepton = 0
AntiLepton = -1
Always conserved in interactions
What is a Muon
A heavy electron
Will eventually decay into an electron
What is a strange particle
Give an example of one
A particle produced by the strong nuclear interaction but decays by the weak interaction
eg. A Kaon, which decays into a Pion by the weak interaction
Has a strange quark in it
They have strangeness
What is strangeness
A property of a strange particle
Strange = 1
Not strange = 0
Antistrange = -1
Strangeness can only be changed in a weak interaction
It is conserved in all interactions but weak. So strange particles are produced in pairs
What is a quark
A fundamental particle that makes up hadrons
What is the quark structure of a Proton
uud
What is the quark structure of a Neutron
udd
What is conserved in every particle interaction
Energy
Momentum
Charge
Baryon No.
Lepton No.
What is the Photoelectric Effect
The photoelectric effect is where photoelectrons are emitted from the surface of a metal after light above a certain frequency is shone on it.
What is Threshold Frequency
Minimum frequency of light required to cause the electric effect
How does Threshold Frequency show the Wave-Particle Duality of Light
If light was a wave, frequency of light should be able to cause photoelectric emission as the energy absorbed by each electron will gradually increase with each incoming wave.
So Threshold Frequency shows that
- Light travels in Photons
- Each electron can only absorb 1 photon
- If the intensity of the light is increased and the frequency is above the threshold, more photoelectrons are emitted per second.
What is the work function of a metal
the minimum energy required for electrons to be emitted from the surface of a metal.
Denoted by Ø
What is stopping potential
s the potential difference you would need to apply across the metal to stop the photoelectrons with the maximum kinetic energy.
Define light intensity
Joules of energy transferred to a surface a photons per second
What is excitation
Occurs when the energy gained from a collision with a free-electron causes an electron to move up an energy level in an atom
What is ionisation
Occurs when the electron in the atom gains enough energy from a collision with a free electron to leave the atom.
Will occur if the energy of the free electron is more than the ionisation energy
What will usually happen after excitation
The electron will return back to its original energy level and release the energy it initially gained in the form of a photon
This is de-excitiation
How does a fluorescent tube produce light
A p.d is made across the tube that has mercury gas in it, so electrons will accelerate through the tube
As they pass through, they collide with mercury atoms, ionizing them, so they release even more free electrons.
All these free electrons then collide with the mercury atoms, exciting and de-exciting them so photons of UV light are released.
Phosphorous fluorescent coating of the tube absorbs the photons, exciting/de-exciting its electrons so they release photons of visible light
Define the electron volt
How do you convert
The energy gained by one electron when passing through a potential difference of 1 volt.
1eV = 1.6x10-19J
How to produce a line emission spectrum
Shine the light produced from a fluorescent tube through a diffraction grating
. Each line in the spectrum will represent a different wavelength of light emitted by the tube.
As this spectrum is not continuous but rather contains only discrete values of wavelengths of photons that diffracted differently
What does a line emission spectrum show
Different differences of energy between 2 energy levels in an atom
The energy of each photon produced is caused by an electron losing energy by moving between energy levels
The fact that the photons have different energies shows the difference between energy levels is not constant
What is a line absorption spectrum
How is it produced
A continuous spectrum of all wavelengths of light, but with black lines
When white light passes through a cool gas.
Photons of a certain energy (came from electrons moving between the same 2 energy levels) are all absorbed, leaving no light at that wavelength
How is Light shown be a wave
Diffraction
Interference
How is light shown to be a particle
Photoelectric effect
How are electrons shown to be a wave
Electron diffraction
What is the De Broglie Hypothesis
The wavelength of a particle is determined by its momentum
De Broglie Wavelength = Planck’s const. ÷ Momentum
How is Momentum and amount of diffraction linked
A higher momentum decreases a particles De Broglie Wavelength which decreases the amount of diffraction
So the circular diffraction pattern will have a smaller diameter
