particles and em radition

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jusjesjisjos

Cards (93)

what are some baryon quark combinations? 
p = uud
/p = /u/u/d

n = udd
/n = /u/d/d

Λ0 = uds
/Λ0 = /u/d/s

Σ+ = uus
/Σ+ = /u/u/s

Σ0 = uds
/Σ0 = /u/d/s

Σ- = dds
/Σ- = /d/d/s

/ = anti
what are the meson quark combinations?
π⁰ = u/u or d/d
π⁺ = u/d
π⁻ = d/u
K⁰ = d/s
K⁺ = u/s
K⁻ = s/u

/ = anti
what is electron proton collision? 
a proton and an electron collide, exchanging a W- boson, the electron turns into a neutron and electron neutrino

p + e− → n + νe
what is electron capture and its equation? 
where a proton captures an inner shell electron and turns into a neutron and electron neutrino, exchanging a W+ boson in the process

p + e− → n + νe
what are the muon decay equations? 
μ− → e− + /νe + νμ
μ+ → e+ + νe + /νμ

/ = anti
what is the power of laser beam equation?
power of beam = nhf
n = no. of photons in beam passing fixed point each second
what are electromagnetic waves?
photons consisting of electric and magnetic waves in phase and at right angles to each other (radio -> microwave -> infrared -> visible -> UV -> x-rays -> gamma rays)
what are fundamental particles?
particles that can not be broken down into smaller components
what are the characteristics of gravity?
weakest force, infinite range, affects all particles with mass
what are the characteristics of the electromagnetic force?
infinite range, virtual photons as exchange particles, affects only charged particles
what are the characteristics of the weak force?
10^-18m, W+, W-, Z0 bosons as exchange particles, affects all particles
what is the minimum energy of a photon required to make a proton-antiproton pair?
2 x proton rest mass
2 x 938.257 = 1876.514 MeV
how was the neutrino's existence hypothesised?
the energy of particles after beta decay was lower than before, a particle with 0 charge (to conserve charge) and negligible mass must carry away this excess energy, antineutrinos were then discovered 20 years later from their interaction with cadmium nuclei in water
what are gauge bosons?
the exchange particles that transmit the four fundamental interactions between particles
what is a baryon?
a class of hadron, that is made up of three quarks, the proton is the only stable baryon
what are the four wave properties?
reflection, refraction, diffraction, interference
what is the de broglie wavelength equation?
λ = h/mv
mv is momentum
what is wave particle duality?
the concept that all particles exhibit properties of both waves and particles, and vice versa
what can be used as evidence for discrete energy levels in atoms?
line emission and absorption spectra, as the lines appear at discrete points which show where a light photon of specific frequency and wavelength has been absorbed or emitted, this shows electrons can only absorb an exact amount of energy to be excited to the next discrete energy level
how does a fluorescent tube work?
high voltage applied across mercury vapour accelerates fast moving free electrons which collide with the mercury atoms, mercury electrons are excited and then return to the ground state, releasing a uv photon, the tube's phosphorus coating absorbs the uv photons and its electrons are excited, they cascade down the energy levels and emit visible light photons.
if a photon has a higher frequency than the threshold what occurs?
the electron is liberated and the remaining energy is the kinetic energy of the electron
why does a photon need to have a minimum energy to liberate an electron?
the photon's energy must be greater than the work function in order to emit an electron
when does excitation occur?
when a free electron collides with an orbital electron or when an electron absorbs a photon (transferring energy to it)
what is a gold leaf electroscope?
a device with a metallic stem and a gold leaf that can be used to identify and measure electric charge
what is the threshold frequency equation? 
frequency = work function / planck's constant (f = Φ/h)
what is photon energy equation?
E = hf = hc / λ (E ∝ 1 / λ)
what is the photoelectric equation?
planck's constant x frequency = work function + maximum kinetic energy of the photoelectrons (hf = Φ + Ek(max))
what is the maximum kinetic energy equation?
Ek(max) = eVs
Vs = stopping potential
e = charge of an electron
derived from energy = charge x voltage
what is the work function?
minimum energy required to remove an electron from a metals surface
what is stopping potential?
minimum potential difference required to stop the highest kinetic energy electrons from leaving the metal plate in the photoelectric effect
what is a photon?
a packet of energy (particle of light) - have energy that's directly proportional to frequency
what is ionisation?
process of an atom losing an orbital electron and becoming charged
what is the ground state?
the lowest allowable energy state of an atom & most stable
what is excitation? 
process of an electron taking in exactly the right quantity of energy to move to a higher energy level, an electron de-excites afterwards and moves down in energy levels, releasing a photon
what are energy levels?
defined and distinct energies at which electrons can exist in an
atom - they can''t exist between
what is an electron-volt?
work done to accelerate an electron through a potential
difference of 1v
what is electron diffraction?
spreading of electrons as they pass through a gap similar to the magnitude of their de broglie wavelength - evidence for wave-like properties of particles
what are the failures of wave theory?
threshold frequency - change of intensity had no effect below the threshold frequency
intensity independence - maximum kinetic energy didn't increase with intensity
what is the wave theory of light?
energy transferred per second should determine the energy transferred to the electrons (max kinetic energy should increase with intensity, not frequency)

energy should be spread out evenly across the surface of the metal (energy absorbed by each electron would gradually increase so that after a while the electrons would have enough energy to be emitted)

this is not actually the case
what is threshold frequency?
the minimum frequency of light required to produce the photoelectric effect