Particles and quantum ⚛ Flashcards
PROTON
Charge = 1.6 x 10^-19
Relative charge = +1
Mass = 1.67 x 10^-27
Relative mass = 1
Specific charge = 9.58 x 10^7
NEUTRON
Charge = 0
Relative charge = 0
Mass = 1.67 x 10^-27
Relative mass = 1
Specific charge = 1.76 x 10^11
ELECTRON
Charge = -1.6 x 10^-19
Relative charge = -1
Mass = 9.11 x 10^-31
Relative mass = 0.0005
Specific charge = 1.76 x 10^11
Strong nuclear force
Attractive up to separations of 3fm
Repulsive below 0.5fm
Unstable nuclei
Too many protons, neutrons or both
So SNF can’t keep them stable so the nuclei decay in order to become stable
Alpha decay
Occurs in large nuclei
Too many protons and neutrons
• Protons decreases by 2
• Nucleon number decreases by 4
Beta minus decay
Too many neutrons
• Proton number decreases by 1
• Nucleon number stays the same
Antiparticle
Same rest energy and mass but opposite in all other properties
Photon
How electromagnetic waves travel in packets
Transfer energy and have no mass
Photon energy
Directly proportional to the frequency of electromagnetic radiation
E = hf = hc/lamda
(h = planck constant 6.63 x 10^-34 Js)
Annihilation
Where particle and antiparticle collide and their masses are converted to energy
The combined energy and ke is released as 2 photons moving in opposite directions to conserve momentum
Pair production
Where a photon is converted into an equal amount of matter and antimatter
Can only occur when a photon has energy is greater then the total rest energy of both particles
any excess energy is converted into ke of the particles
Strong interaction
Exchange particle : Gluon
Range : 3 x 10^-15
Acts on : Hadrons
Weak interaction
Exchange particle : W boson (-&+)
Range : 10^18
Acts on : all particles
Electromagnetic interaction
Exchange particle : Virtual photon
Range : Infinite
Acts on : Charged particles
Gravity interaction
Exchange particle : Graviton (dw)
Range : Infinite
Acts on : Particles with mass
Weak nuclear force interactions
Beta decay, electron capture and electron-proton collisions
Electron capture
p + e^- —–> n + ve
(W+)
Electron-proton collision
p + e^- —–> n + ve
(W-)
Beta-plus decay
p —–> n + e^+ + ve
(W+)
Beta-minus decay equation
n —–> p + e^- + anti ve
(W-)
Hadron vs lepton
Leptons ARE fundamental and DO NOT experience strong interaction
Hadrons are made of quarks and therefore ARE NOT fundamental
Hadrons subgenre
Separated into baryons, antibaryons and mesons
Baryons formed of 3 quarks
Antibaryons formed of 3 antiquarks
Mesons formed of a quark and antiquark
Meson example
Pion
Kaon
Lepton example
Electron
muon
electron neutrino
Baryon examples
Proton
neutron
Conservations in particle interactions
Baryon number
lepton number
charge
strangeness
momentum and energy
Strange particles
Produced by strong nuclear interaction but decay by the weak one
Kaons (strangeness +1) decay into pions by the weak interaction
Strangeness can only change in the weak interaction
UP quark
Charge : + 2/3 e
Bryon number : + 1/3
Strangeness : 0
DOWN quark
Charge : - 1/3 e
Bryon number : + 1/3
Strangeness : 0
STRANGE quark
Charge : - 1/3 e
Bryon number : + 1/3
Strangeness : -1
Meson quark combination
- Pi0 = up anti=up or down anti-down (0)
- Pi+ = up anti-down (+1)
- Pi- = anti-up down (-1)
- Kaon0 = down anti-strange (0)
- Kaon+ = up anti-strange (+1)
- Kaon- = anti-up strange (-1)
Photoelectric effect
Where photoelectrons are emitted from the surface of a metal after light above a certain frequency is shone on it (threshold frequency)
Threshold frequency explanation
EM waves travel in discrete packets therefore a photoelectron is only emitted if the frequency is above the threshold frequency
Each electron can absorb a single photon, therefore photoelectrons are only emitted if THF is met
Intensity increase = more photoelectrons emitted
Work function
minimum energy required for electrons to be emitted from the surface of a metal
Stopping potential
Potential difference needed across the metal to stop the photoelectrons with the max KE
Photoelectric effect equation
E = hf = work function + Ek
Electrons in atoms
Only exist as discrete energy levels
Gain energy from collisions with free electrons which causes them to move up energy levels which is known as excitation
Or they gain enough energy to be removed from the atom entirely which is known as ionisation
When does ionisation occur
If the energy of the free electron is greater than ionisation energy
Electron excitation
Will quickly return to original energy level (ground state) and therefore releases the energy it gained in the form of a photon
Fluorescent tubes
*High voltage applied across the mercury vapour accelerates fast moving free electrons which collide with mercury atoms
*Mercury electrons are excited and move back to ground state, emitting a UV photon
*The tube’s phosphorus coating absorbs the UV photons and its electrons excite. They then cascade down the energy levels and release visible light photons
Electron volt
Energy gained by one electron when passing through a potential difference of 1 volt
De Broglie wavelength
lambda = h/mv
Photon energy equation
E = hc/lambda
Ionising energy
minimum energy required to remove the most loosely bound electron of an isolated gaseous atom, positive ion, or molecule
