particles and radiation Flashcards
what mediate electromagnetic force
virtual particles/ photon
carrier of weak nuclear force
w and z bosons
carrier of strong nuclear force
gluon/ pion
what is the range of the strong nuclear force
3fm / 3x10-15m
speed of light
3x10^8 m/s
what is conserved in pair production
energy
momentum
charge
lepton number
baryon number
give equations for annihilation
2mc^2=2hfmin
what happens in annihilation
a particle and its antiparticle collide
their mass is transformed into two high energy gamma photons
what is equal and opposite about the two photons created in annihilation
equal and opposite charge
through what process can gamma photon convert to an electron and positron
pair production
which constituent of the atom has the largest charge-to-mass ratio
electron
state a difference between a photon and an exchange particle of the weak nuclear force
photon rest mass=0 , w bozon rest mass >0
photon has infinite range, bosons have a finite range
whats the antiparticle of the electron
positron
what is the quark composition of k+
up
anti strange
what is the quark composition of k-
anti up
strange
what is the quark composition of k0
down
anti strange
which hadron has quark composition sss
omega
what are mesons made of
1 quark and 1 antiquark
are leptons fundamental
yes
which particle do all leptons decay to
electrons and neutrinos
whats a nuclide
type of nucleus with a set number of protons and neutrons
what is planks constant, h
6.63 x10 ^-34 J
frequency equation
f= wave speed/ wavelength
what is excitation
the process of an electron taking on exactly the right quantity of energy to move to a higher energy level
what is the ground state
the most stable energy level that an electron can exist in
what is ionisation
the process of an atom losing an orbital electron and becoming charged
what do kaons decay into
pions
what is a nucleon
a proton or neutron
what is stopping potential
the minimum potential difference required to stop the highest kinetic energy electrons from leaving the metal plate in the photoelectric effect
what are strange particles produced through and how do they decay
particles that are produced through the strong interaction
but decay through the weak interaction
what is the strong nuclear force
a force that acts between nucleons in a nucleus to keep it stable.
it is attractive at distances up to 3fm and repulsive at separations less than 0.5 fm
what is threshold frequency and what is it’s equation
the minimum frequency of photons required for photoelectrons to be emitted from the surface of a metal plate through the photoelectric effect
it is equal to the metal’s work function divided by Planck’s constant
what is work function
the minimum energy required to remove an electron from a metal’s surface
(by overcoming the metallic bond holding it in the metal)
what is the nucleon number
the sum of the number of protons and neutrons in a given nucleus
(A)
what is an energy level
defined and distinct energies at which electrons can exist in an atom. An electron cannot exist between energy levels
what is beta+ decay?
what particles are emitted?
a proton turning into a neutron
emitting a beta+ particle (positron) and a neutrino
what is beta- decay
the process of a neutron inside a nucleus turning into a proton, and emitting a beta-minus particle (an electron) and an antineutrino
are electromagnetic waves transverse or longitudinal
transverse
what phenomenon can be used to show that light behaves as a particle
the photoelectric effect
what is the photoelectric effect
when light above a particular frequency is shone on a metal, electrons are released, called photoelectrons
what equations is used to determine the energy of a photon
E = hf = hc/λ
why does a photon need to be of a minimum frequency to liberate an electron?
the energy of the photon is determined by its frequency, the photon’s energy must be greater than the work function (energy needed to break the bonds holding the electron) in order for an electron to be emitted
what happens when a photon has frequency higher than the threshold frequency
the electron will be liberated and the remaining energy is the kinetic energy of the electron
what is the effect of increasing light intensity
more photons incident on the metal each second
but as each photon carries the same amount of energy as before
it still does not contain enough energy to liberate an electron
so there will be no effect
what is he photoelectric equation
hf = ϕ +Ek(max)
what is an electron volt
the kinetic energy of an electron that has been accelerated from rest through a potential difference of 1V
how do you convert eV to joules
1eV x 1.6 x10^-19 = 1J
how do you convert joules to electron volt
1J / 1.6 x10^-19 = 1eV
how does a fluorescent tube work
high voltage is applied across mercury vapour which will accelerate fast moving free electrons that colllide with mercury atoms.
mercury electrons are excited and then return to ground state which releases a UV photon.
the tubes phosphorus coating absorbs UV photons and as its electrons are excited, they cascade down the energy levels and emit visible light photons.
what can be used as evidence for the 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.
What is wave particle duality?
All particles have both particle and wave properties, waves can have particle properties e.g. light acts as a particle in the photoelectric effect and as a wave when it is diffracted.
What is the equation for de Broglie wavelength?
lamda = h/mv
Where mv is momentum.
What is a pion?
What is its quark structure?
a meson that consists of an up or down quark and an up or down antiquark
What is a positron?
a particle of antimatter that is the antiparticle of the electron
what is a muon?
a lepton which is negatively charged and has a greater rest mass than the electron
does an electron or a muon have the greater rest mass?
muon
what is a kaon?
a meson that consists of a strange quark or antiquark and another quark or antiquark
how do leptons interact?
through the weak interaction
what are free elctrons?
electrons in a conductor that move freely inside the metal because they are not attached to a particular atom
what is the work function?
the energy required by an electron to overcome the metallic bond holding it in the metal
what is an electron volt?
the kinetic energy of an electron that has been accelerated from rest through a potential difference of 1V
what can scientists find out from isotopic data?
approximate age of archaeological finds made from dead organic matter (eg wood and bone)
how do scientists use isotopic data to approximate the age of dead organic matter?
find the percentage of radioactive carbon-14 that’s left in the object. overtime the amount of carbon-14 in them decreases as it decays to stable elements. the percentage or carbon which is radioactive carbon 14 ( taken in from the atmosphere) is the same in most living things
why must the strong nuclear force be attractive and stronger than the electromagnetic force?
to old the nucleus together
which particle was proposed to account for missing energy in beta decay?
neutrino
(actually an antineutrino for beta minus decay)
which part of the electromagnetic spectrum has the highest frequency?
gamma rays
which part of the electromagnetic spectrum has the largest wavelength?
radio waves
which part of the electromagnetic spectrum has the greatest energy?
gamma rays
what is the same for a particle and its corresponding antiparticle?
mass and rest energy
what is different for a particle and its corresponding antiparticle?
charge, its oppositew
what is the mass and rest energy for neutrinos and antineutrinos?
zero
who created a theory saying energy can turn into mass and vice versa?
Einstein
what is E0 (little zero)
rest energy
what is an application of annihilation?
PET scanner
what are two classes of hadrons?
baryons and mesons
what are two types of meson?
pion and kaon
what is the only stable baryon?
proton
what will all other baryons eventually decay into?
proton
what will a muon decay into?
electron
is a kaon a strange particle?
yes
what are strange particles always created in?
pairs
in what interaction is strangeness conserved?
strong interactions
what can strangeness change by in weak interactions?
0, +1, -1
particle physics relies on the
collaborative efforts of …
of large teams of scientists and
engineers to validate new knowledge
what are 3 properties of quarks and antiquarks?
charge,
baryon number,
strangeness
what is formed in neutron decay?
proton
electron
antineutrino
what is beta decay caused by?
weak interaction
what is the baryon number of an antineutrino?
B= 0
are mesons stable?
no
what is pi0 the antiparticle of?
itself, pi0
which mesons are heavier?
kaons
which mesons are more unstable?
kaons
what do kaons decay into?
pions
what are pions the exchange particle of?
strong nuclear force
what are cosmic rays?
high-energy particles from space that are constantly hitting earth
what is evidence for
transitions between discrete energy levels in atoms?
line spectra (eg of atomic hydrogen)
what are exchange particles also know as?
virtual particles
what do virtual particles do?
exist for a short time where they transfer energy, momentum and other properties between interacting particles.
what are the exchange particles of the electromagnetic force?
virtual photon
what causes electrostatic repulsion between two protons?
the exchange of virtual photons
what is the group name for exchange particles of the four fundamental forces?
gauge bosons
what are the exchange particles of the strong nuclear force?
pions
what particles are affected by the strong nuclear force?
hadrons only
what property must particles have to be affected by the electromagnetic force?
must be charged
what types of particles are affected by the weak nuclear force?
all types
what are the exchange particles for the weak nuclear force?
W+, W- bosons
heavier exchange particles have a ________ range
shorter
why does the electromagnetic force have infinite range?
because its gauge boson/exchange particle is the photon which has zero mass
what can be said about the range of the weak force?
very short range
what happens when two particles with equal charge get close to each other?
they repel with the exchange particle being a virtual photon
