Particles and Radiation (Quantum Phenomena) Flashcards
What shows Light is a Wave?
Youngs’ double slit experiment
Constructive and destructive interference
What is the Photoelectric demonstration?
Shining high frequency waves at a metal.
Current is produced due to ionisation of atoms.
Created current is detected by an electroscope.
How does the Photoelectric demonstration show light is not a Wave?
A waves energy is depends on amplitude, not frequency.
Brighter light has more energy, therefore any frequency would provide enough energy, howebver this doesn’t happen
Define Work Function?
The minimum amount of energy required to move an electron to infinity from an atom
What is the symbol and units of Work Function?
Symbol: ϕ
Unit: J
What affects the number of Electrons emitted?
Intensity of light
As greater intensity means more photons
What affects the Maximum Kinetic Energy of an emitted Electron?
Frequency of light
As greater frequency means more energy
What is the equation for energy of a particle?
E = fh = hc/λ E = energy f = frequency h = planck constant c = speed of light λ = Wavelength
What is Plancks Constant?
6.63 x 10^-34 Js
What is the equation for Maximum Kinetic Energy?
E = hf - ϕ
What is the Threshold Frequency?
The minimum frequency of a photon such that an emitted electron can “just” escape.
(the minimum frequency that will produce the photoelectric effect)
What is the equation for the Threshold Frequency?
f = ϕ/h
When does the Photoelectric effect happen?
if Incident frequency ≥ Thershold frequency
What is Stopping Potential?
The potential difference required to stop the current produced b the photoelectric effect from flowing
How is Stopping Potential calculated?
Using a Vacuum Photocell, which is a vacuum chamber with a curved and a flat plate inside.
When the Photoelectrons are released thye will travel from the curved plate to flat.
A power supply is added to the circuit and incresed till the current stops flowing.
What is the equation for Stopping Potential?
eVs = E e = Charge on an electron (1.6 x 10^19 C) Vs = Stopping potential E = Maximum kinetic energy
What is an Energy Level?
A discrete quantity of energy in which an electron can exist in an atom
What is an Electron Volt?
The energy which an electron have
What is 1 eV equal to?
1eV = 1.6 x ^-19 J
What is the Ground State?
The lowest energy level
n=1
It has the lowest energy
Why are Energy Levels negative values?
Energy is required to move the electron to infinity.
At infinity the electron has no energy.
Therefore to increase to 0 they must be negative
Define Excitation?
When electrons move up the energy ladder
What happens when an electron is at n=∞?
The electron leaves the atom
Ionisation
What is the symbol for a Photon?
γ
Lower case Gamma
What causes Excitation?
Free electrons colliding with the electron in an atom, this transfers energy (conservation of momentum), is enough energy is transfered ionisation occurs.
Photons with the exact energy be transformed to energy when colliding with the electron
What happens when an electron de-excites?
When the electron decreases in energy levels a photon is released, with the same energy as the energy change of the electron
What experiments show the Wave and Particle like nature of Electrons?
Wave: Electron Difraction
Shining a beam of electrons through an atomic lattice creates an interference pattern.
Particle: Electron Deflection
A beam of electrons can be deflected by an E or B field, showing it has charge. Therefore a particle
What experiments show the Wave and Particle like nature of Light?
Wave: Youngs’ Double Slit
Shows super-position
Particle: Photoelectric
Shows photons are individual packets of energy
what is the equation for De Broglle Wavelength?
λ = h/ρ = h/mv λ = De Broglie Wavelength h = Planck Constant ρ = Momentum m = Mass v = Velocity
Define Nucleon?
A particle in the nucleus
Proton or Neutron
Define Isotope?
Atoms which have the same atomic number but different atomic mass
What is roughly the size of an Atom, Nucleus and wavelength of Visable light?
Atom: 10^-10 m
Nucleus: 10^-15 m
Visable light: 10^-7
What is Specific Charge?
The ratio of a molecules Charge to its Mass
How is Specific Charge Calculated?
Q/m
Q = Charge in Coulombs
m = Mass in kg (EXCLUDING ELECTRONS)
Units: Ckg^-1
What is Alpha Decay?
When an atom emitts an alpha particle (Helium nucleus).
Charge of the atom decreases by 2
Mass of the atom decreases by 4
What is Beta Decay?
When a neutron decays into a proton and releases a Beta particle (electron)
Charge of the atom increases by 1
Mass of the atom remains unchanged
Gravity
What is the Range, Relative strength and what it acts on.
Range: Infinite
Relative strength: 10^-39
Acts on: Mass/Energy (as E=mc²)
Example: Stars
Electromagnetic
What is the Range, Relative strength and what it acts on.
Range: Infinite
Relative strength: 10^-2
Acts on: Charge
Example: Electricity
Strong Nuclear
What is the Range, Relative strength and what it acts on.
Range: 10^-15
Relative strength: 1
Acts on: Quarks
Example: Fusion/Fission
Weak Nuclear
What is the Range, Relative strength and what it acts on.
Range: 10^-18
Relative strength: 10^-5
Acts on: Everything
Example: Radioactivity
What does the Strong Nuclear Force do?
Binds the Nucleus and maintains its stability.
As attracts up to 3 fermimeters (3 x 10^-15)
And repels beneath 0.5 fermimeters (0.5 x 10^-15)
Define Antiparticles?
Antiparticles have the same rest mass as their corresponding particles but all other properties are opposite. (Charge, Baryon number, Lepton number, Strangeness)
What Particles are their own Antiparticles?
Photon Pi Nought (uū)
What is Annihilation?
When a particle-antiparticle pair produce two high energy Photons (to conserve momentum).
eg. n̄ + n → γ + γ
What is Pair Production?
When a high energy photon produces a particle-antiparticle pair.
eg. γ → n̄ + n
How can the energy of the Photon in Pair Production be calculated?
The rest energy of the Particle and Antiparticle combined
What is Beta Minus Decay?
Production of Beta Particle (electron/beta radiation)
Neutron → proton + electron + anti electron neutrino
What are the properties of Leptons?
Don’t interact with strong nuclear force
Lepton number is conserved
Fundamental particles
Decay to electron types to become more stable
Give examples of Leptons?
Stable: Electron, Positron, Electron Neutrino, Positron Neutrino
Unstable: Muon (anti and neutrino and antineutrino versions)
Tau (anti and neutrino and antineutrino versions)
What are the properties of Hadrons?
Interact through strong nuclear force
Not fundamental
Sub groups are Baryons and Mesons
What are properties of Baryons?
Baryon number is conserved
Made of 3 Quarks
Examples are Proton (stable) and neutron (unstable)
What are Properties of Mesons?
Strangeness is conserved
Made of Quark and Antiquark
Deacy to pions to become more stable
Example is Pion+
Name the Quarks?
Up Down
Charm Strange
Top Bottom
Why do Quarks have Charges based on thirds?
because energy system is based off of particles such as protons which have 1, therefore as they make up these particle tey must have less than one
Why are Singular Quarks not possible?
The energy to split quarks apart is enough to create new quarks. which then pair with the now split quarks, meaning they remain a pair.
What is conserved in Strong interactions?
Total number and types of quark
therefore baryon number and strangeness are conserved
What is and isn’t conserved in Weak interactions?
Total number of quarks is conserved (therefore baryon number is conserved)
Type of quark is not conserved (strangeness is not conserved)
What are Gauge Bosons?
Exchange Particles
eg. γ, w+ and w-
What is the Exchange Particle for EM?
Photons
What is the Exchange Particle in a Weak Nuclear interaction?
W+ (eg proton emits W+ to electon, neutralising both)
W- (eg electron emits W+ to proton, neutralising both)
What is the rest mass of the Gauge Bosons?
Photon: 0 MeV
W+: 80400 MeV
w-: 80400 MeV
