Physics Unit 4

Standard Model

Quarks

Leptons

Gauge bosons

Conservation requirements

Feynman diagram

Symmetry

Anti-top, anti-bottom, anti-strange, anti-charm, anti-up, anti-down

Elementary particles

neutrino, muon, Tau lepton, electron, electron neutrino, tau neutrino

Lepton and Baryon no.

Is not affected by Strong force

crossing

Charge-reversal

time-reversal

involves moving particles between sides of the reaction by turning them into their anti-particles

If all negative charges are swapped with positive charges, a particle interaction should still happen equivalently

The particle interaction that occur can happen in reverse, think l'chatiliers principle from physics

Significance

Conservation laws must be followed

used to predict reactions but doesn't mean it works for all interactions

Violation of symmetry is useful to determine the forces of that reaction

Must be conserved in reactions

Each quark has a Baryon no. of +1/3

Each antiquark has a baryon no. of -1/3

Each lepton has a no. of +1

Each anti-lepton has no. of -1

Top, bottom, strange, charm, up, down

Affected by the strong nuclear force

Conservation of mass

Conservation of charge

Colour must be white

Conservation of Lepton and Baryon numbers

Used to display particle interactions

Guage bosons in centre

Space on y-axis, time on x-axis

The guage bosons mediate the forces in particle interactions

Electromagnetic force: photons

Weak nuclear force: W and Z bosons

Strong nuclear force: Gluons

Gravity force: Graviton

Quantum Theory

black-body radiation

Double-slt experiment

planck's constant

photoelectric effect

models of the atom

hydrogen spectrum

wave-particle duality of light

displays light as a wave

shows the interference pattern as through the slits ehy formed an intereference of dark and light bands

only waves can interfere constructively and destructively, onlywaves can do this therefore light is a wave

evidence fo light as a particle

if you treated light as a wave then a large amount of UV should've been emitted, instead it didn't

the graphs instead had a peak rather than a antompe graph which could only be explained by considering light to be a packet of energy (as a particle)

electrons are only emitted after a threshold frequency is reached

this shows light as a particle as a waves energy is in the intensity , not the frequency, so the frequency of light should not matter

this shows light as a packet of energy, all given to the electron at once, thus if it is enough to overcome the work-function the electron escapes

Ek of e- depends on the frequency of light

From black-body, photoelectric and double slit experiments it shows that light can sometimes behave as a wave and sometimes as packets of energy (particles) so therefore light is considered to be both and thus wave-particle duality

Rutherford's model of the atom: Atoms are empty space with a dense positively charged nucleus in the center and negatively charged electrons that orbit it

limitations of Rutherford model: couldn't explain how electrons are accelerating electric charges that produce EM radiation and lose energy so they are thought to spiral into the nucleus. Could not explain why different atoms have different colours on the spectrum

Is the visible colour spectrum

Wavelengths given by Rydberg equation

These observed spectral lines are due to the electron making transitions between two energy levels in an atom

6.626x10^-34m^2kg/s

Used in black-body radiation when light is a particle