phy unit 3 and 4

Kepler’s first law

all planets move about the sun in elliptical orbits with the sun as one of the foci

Kepler’s second law

a radius vector joining any planet to the sun sweeps out equal areas in equal lengths of time as the closer a planet the faster it moves and vice versa

Kepler’s third law

the square of the time it takes for a planet to complete an orbit of another body is directly proportional to the cube of the planet’s mean distance from the sun

Kepler’s third law equation

T²/r³=T²/r³ and T²/r³=4pi²/GM

electromagnetic wave

perpendicular electric and magnetic fields and do not need a medium, travelling at the speed of light in a vacuum

Einstein’s first postulate

the laws of physics are the same in all inertial frames of reference

Einstein’s second postulate

the speed of light in a vacuum is constant in all inertial frames of reference

black body

object that absorbs and emits all radiation that falls on it

double slit experiment

light is detected as individual photons but the overall pattern demonstrated diffraction, a property of waves. bright bands indication of constructive interference and dark banks indicated destructive interference.

increase temp impact on intensity

increase intensity and amplitude of wave

electron fall

emits photon

electron goes up

absorbs photon

Rutherford’s model

dense positively charged nucleus surrounded by orbiting neg. electrons

limitations of Rutherford’s model

1. charged particles radiate energy when they accelerate/orbit and thus should emit energy as they orbit nucleus eventually losing all energy and imploding, but doesn’t happen (why dont they spiral into nucleus

2. excited gas atoms emitted light in discrete lines not in continuous spectrum like expected (why electrons dont continuously emit energy and emission spectra only in discrete lines)

continuum expected spectra

all excited atoms where white light is diffracted through a prism

emission spectra (hot gas)

observed when light from excited atoms in gas state is diffracted through a prism and is unique for each atom

absorption spectra (cold gas)

weight is passed through cold gas and only specific wavelengths are absorbed and thus removed from the continuum

bohr model

electrons exist in fixed stationary states without emitting energy and electrostatic force pulls electron towards nucleus and e- intrinsic energy prevents from leaving state. electron absorb or emit photon with energy when change state

bohr model strengths and limitation

1. electrons dont emit energy in stable energy, thus dont continuously emit energy and wont spiral into nucleus

2. emission/absoprtion spectra explained by specific energies required to jump between energy levels

   1. cannot accurately describe observation for multi-electron atoms, only predicted transitions for H (1-electron atom)

Lyman series

between n=1 and higher, ultraviolet light

Balmer series

between n=2 and higher, visible light

Paschen series

between n=3 and higher, infrared light

de Brogile

proposed that particles have an associated wavelength

fundamental particle split up

fermions - quarks and leptons

bosons - photon, gluon, w boson, z boson

+2/3 charge quarks

up, charge, top

-1/3 charge quarks

down, strange, bottom

trend as increase in flavour

increases in mass and decreases in stability thus less time alive and more likely to degrade down to 1st flavour

-1 charge leptons

electron, muon, tau

neutral charge neutrino

electron neutrino, muon neutrino, tau neutrino

baryon

made up of three quarks eg: proton uud, neutron udd

meson

made up of one quark and antiquark and charge must add up to an integer

antiparticles

anti up, anti down etc represented by dash and flipped charge (neg to pos) but no change in mass eg: anti proton -1 charge (2xantiup 1xantidown)

photon (gamma symbol)

carrier of electromagnetic force passed between particles

gluon

mediate strong force, glues everything together eg” gluon hold two up quark together

w± boson

mediate weak nuclear force responsible for labour change like from u to d ± depend on beta decay

z boson

mediate weak nuclear force and charges

translational symmetry conserves

momentum

rotational symmetry conserves

angular momentum

time symmetry conserves

energy

electron-electron Feynman diagram

electron-positron Feynman diagram

proton-neutron beta pos. Feynman diagram

bha bha Feynman diagram

neutron-proton beta neg. Feynman diagram

flux density

flux/area

faraday’s law

a change in mag field through a region will produce an electric field

Lenz’s law

the direction of an induced electric current will oppose the change in circuit or mag field that produces it

explain why objects with mass cannot travel at the speed of light

due to relativistic momentum formula, if v=c the bottom of the fraction becomes 0 making momentum at c undefined and not possible. then W=F x s is the time derivative of momentum and if momentum is undefined at c, then F is also defined and thus work is also undefined and impossible to achieve

gravitational field

region of space around object within other objects with mass experience gravitational force of attraction

electric field

region of space around object within other objects with charge experience attractive or repulsive electrostatic force

field lines

indicate direction and strength - more lines=stronger

potential difference

change in substance’s electric potential energy

electric potential energy

property of charge experiencing electric field

zero magnetic flux

surface parallel to field lines

max magnetic flux

surface perpendicular to field lines

flux density

how much of magnetic field is pointing in perp direction to surface

electromotive force

diff in potential that gives a change in current=voltage

magnet moving towards solenoid

current induced to the left

magnet moving away from solenoid

current induced to the right

faraday’s law

change in flux produces emf

Lenz’s law

direction of induced current is opposite to what caused it

how is Lenz’s law match principle of conservation of energy

mechanical energy is converted into electrical energy to oppose charge

what is a transformer

two coils wrapped around soft iron core, AC is passed through primary coil and secondary coil steps up or down voltage

transformer formula

Vp/Vs=np/ns

ideal transformer formulas

P=VI, Pp=Ps, VpIp=VsIs

step up transformer

Vs>Vp, Ns>Np, current decreases

step down transformer

Vs<Vp, Ns<Np, current increases

how transformers work in terms of faraday’s

AC current in primary leads to change in mag field which leads to change in flux through secondary coil inducing EMF

electromagnetic radiation

energy transmitted at speed of light through oscillations in electric and magnetic fields

muon problem and why it suggests newtonian physics is incomplete

cosmic rays colliding with particles at earth’s upper atmosphere producing muons that are unstable with short lifetimes. newtonian physics predict that it will decay high in the atmosphere but muons are detected on earth’s surface suggesting incomplete at speeds close to light