Particles and Quantum Phenomena Flashcards
isotope
atoms with the same number of protons but a different number of neutrons
equation for specific charge
charge/mass
units of specific charge
C kg ^-1
particle with greatest specific charge
electron
what is an alpha particle
2 protons and 2 neutrons
beta minus particle
a fast moving electron formed through the conversion of a neutron to a proton
beta plus particle
a fast moving electron formed through the conversion of a proton to a neutron
gamma particle
a high energy photon
nuclear equation for alpha decay
azX –> a-4 z-2 Y + 42α
nuclear equation for beta minus decay
azX –> a z+1Y + 0-1β- + v-e (anti)
nuclear equation for beta plus decay
azX –> a z-1Y + 0+1β+ ve
need for neutrinos
conservation of lepton number and energy. they have zero charge and nearly zero mass
feynman diagram beta minus decay
n→p ; W- ; v-e and β-
feynman diagram beta plus decay
p→n ; W+ ; ve and β+
feynman diagram electron capture
p→n ; W+ ; e→ve
feynman diagram for proton electron capture
p→n ; W- ; e→ve
axes of a feynman diagram
vertical axis - time
horizontal axis - space
forces and corresponding exchange particles
strong force - gluon or pion
weak force - W boson
electromagnetic force - virtual photon
gravitational force - graviton
strong nuclear force function and ranges
- keeps nucleus stable
- attractive up to 3 fm
- repulsive up to 0.5 fm
- very short range
can quarks change type
only in weak interaction
pair production
- when a gamma photon changes into a particle and its corresponding antiparticle (move in opposite directions)
- only happens if the energy of the photon > 2mc^2 (rest mass)
annihilation
when a particle and its antiparticle meet, they destroy each other and release 2 gamma photons travelling in opposite directions with the energy of the photons equivalent to the mass of the 2 particles
anti matter
particles with the same rest mass but equal and opposite charge as its corresponding particles
what do exchange particles transfer
- momentum
- energy
- force
- charge (in weak interactions)
difference between hadrons and leptons
hadrons experience the strong force, leptons do not
hadron subgroups
baryons and mesons
baryon
- 3 quarks (baryon) or 3 antiquarks (antibaryon)
- strangeness = 0
meson composition
- quark and anti-quark pair
- pions or kaons
- strangeness = 0 (pion) or +- 1 (kaon)
quark composition of protons
uud
quark composition of neutrons
udd
quark composition of anti proton
anti up, anti up, anti down
quark composition of anti-neutron
anti up, anti down, anti down
quark composition of pions
π⁺ - ud- up, anti down
π⁻ - u-d anti up, down
π° - u-u, or d-d up, anti-up or down, anti-down
quark composition of kaons
K⁺ - us- up, anti-strange
K° - ds- down, anti-strange
K°− - sd- strange, anti-down
K⁻ - su- strange, anti-up
what do Kaons decay through
weak interaction
what do baryons decay into
protons
most stable baryon
proton
what is conserved in weak interaction
- Energy
- Momentum
- Charge
- Baryon Number
- Lepton Number (electron/muon)
what is conserved in strong force
- Energy
- Momentum
- Charge
- Baryon Number
- Lepton Number (electron/muon)
- strangeness
what is a strange particle
a particle that contains at least 1 strange quark or antiquark
characteristics of a strange quark
- it has a strangeness of -1
- produced through strong interaction
- decay through weak interaction
the photoelectric effect
shining light of a sufficiently high frequency onto the surface of a metal will result in the metal emitting (photo)electrons
conclusions from the photoelectric effect
- no photoelectrons are emitted for radiation with a frequency < threshold frequency
- the photoelectrons emitted have a range of kinetic energies from zero to maximum which are unaffected by the intensity of the light
- the number of photoelectrons emitted per second is proportional to the intensity of the radiation
wave theory
energy carried by light is proportional to intensity and is spread evenly over the wavefront so that each free electron gains a bit of energy at a time until all of them leave the metal
einstein’s model of light
EM waves exist in discrete packets called photons and each photon has a one-on-one, particle like interaction with an electron in a metal surface, to which it transfers all its energy hence the work function
work function
minimum energy required to liberate the least bound electron from the surface of a metal
work function units
joules
threshold frequency
minimum frequency needed to remove the least bound electron from the surface of a metal
the terms hf, Φ and Ekmax in the photoelectric equation
hf = Φ + Ekmax
hf - photon energy
Φ - work function (see definition above)
Ekmax - maximum kinetic energy of the photoelectron
graph of Ek against frequency
gradient = Planck’s constant
y intersect = work function
x intersect = threshold frequency
the Electron Volt (eV)
the energy gained by an electron when accelerated through a potential difference of 1 Volt
converting between electron Volts and joules
1eV = 1.6 x 10-19 J
excitation
an orbital electron moves up from one energy level to another by gaining a specific quantity of energy
excited atom
atom in which an orbiting electron is raised up to a higher energy level
ionisation (florescence tube)
when an electron is removed from an atom
ionisation energy
minimum energy required to completely remove an electron from an atom in its ground state
ground state of an atom
the lowest energy state of an atom
fluorescence
- fluorescent tubes contain Mercury vapour, across which an initial high voltage is applied
- high voltage accelerates electrons which ionise some mercury atoms producing more free electrons
- flow of electrons collides with mercury atoms exciting electrons to higher energy levels
- excited electrons emit high energy UV photons upon de-excitation which are absorbed by a phosphor coating and lower energy photons are emitted in the visible part of the spectrum
emission/absorption spectrum
cool gases can absorb certain wavelengths of light (absorption spectrum) which can be seen in the emission spectrum
what is wave particle duality
particles behave sometimes as particles and sometime as waves
experiment showing waves behaving as particles
photoelectric effect
experiment showing particles behaving as waves
electron diffraction
momentum
mass x velocity
units of momentum
kgms-1
stopping potential
the potential difference required to stop the fastest moving photoelectrons moving with kinetic energy Ek(max)
particle diffraction effects
a particle will diffract when the size of its de Broglie wavelength is roughly the same size as the object causing the diffraction. max diffraction occurs when they are equal
relationship between momentum and de Broglie wavelength
inversely proportional
de-excitation
when an orbital electron moves down from one energy level to another and a photon is emitted with a frequency dependent on the energy difference
process of hypothesis and validation
- a theory is hypothesised
- the theory undergoes evaluation by other scientists
- the theory is tested by experiments
- it is then validated and assumed true until new conflicting evidence comes along
- this process prevents theories which are clearly false being accepted by the scientific community
isotopic data
the relative amounts of different isotopes of an element found within a substance
