section 1 - particles and radiation. Flashcards
what is an isotope?
an atom with the same atomic number, but different nucleon number - same no. protons, different no. neutrons.
equation for specific charge?
specific charge (of a nucleus) = charge / mass.
proton: (p)
charge (C) : 1.60 x 10^-19
mass (kg) : 1.67(3) x 10^-27
neutron: (n)
charge (C) : 0
mass (kg) : 1.67(5) x 10^-27
electron: (e-)
charge (C) : -1.60 x 10^-19
mass : 9.11 x 10^-31
antimatter?
same: REST MASS + REST ENERGY.
different: CHARGE. (-> exception neutrons + neutrinos (+ antimatter))
neutrino/antineutrino: (v, v^_)
rest mass: 0
charge: 0
is the strong nuclear force attractive or repulsive?
attractive up to 0.5 fm, then repulsive.
what is the max. range of the strong nuclear force?
3-4 fm.
the theory behind strong nuclear force?
in stable atoms, atoms are neither expanding or shrinking. electrostatic repulsion between similar charged nucleons occurs. therefore there must be an attractive force that is short range.
how does alpha decay cause an nucleus to change?
NUCLEON NUMBER: -4
ATOMIC NUMBER: -2
what is the alternate name for an alpha particle?
helium nucleus.
how ionizing is alpha radiation? how penetrating is alpha radiation?
highly ionizing. lowly penetrating (paper stops)
wave speed of the electromagnetic spectrum?
3 x 10^8 m/s
electromagnetic spectrum from longest wavelength to shortest wavelength?
radio, microwaves, infrared, visible, UV, x-rays, gamma rays.
photon energy equation:
photon energy = hf (E = hf)
what is annihilation?
when a particle and its antiparticle collide and their masses are converted into energy (x2 photons).
ANNIHILATION: min. photon energy equation:
2hf (min) = 2E –> hf = E
E = rest energy.
hf = energy of one photon.
ANNIHILATION: NON-min. photon energy equation:
2hf = 2E + 2KE --> hf = E + KE hf = energy of one photon.
what is pair production?
when a photon with SUFFICIENT ENERGY creates a particle and its corresponding antiparticle, and vanishes.
PP: min. energy of photon req. equation:
hf(min) = 2E E = rest energy hf = photon energy
what is the eV –> J conversion?
1eV = 1.60 x 10^-19 J
what types of particles does the strong nuclear force act between?
hadrons - protons and neutrons –> EQUALLY.
what is the weak nuclear force?
force responsible for beta decay.
properties of weak nuclear force?
weak - doesn’t affect stable nuclei.
short range.
what types of particles does the weak nuclear force act between?
all.
what are the four fundamental forces?
1) strong nuclear force.
2) weak nuclear force.
3) gravity.
4) electromagnetic.
what is the exchange particle for electromagnetic force?
virtual photon.
what is the exchange particle for the strong nuclear force?
gluon/pion.
what is the exchange particle for the weak nuclear force?
W bosons (W+ / W- ).
describe what happens to the participants of electromagnetic repulsion?
particles of the same charge come close to each other. exchange a virtual photon. move off it opposite directions. no change to particle. (often e-)
describe what happened to the participants of beta minus decay?
NEUTRON –> PROTON.
emits a BETA MINUS particle (e-) + ELECTRON ANTINEUTRINO.
during beta minus decay, how does the quark composition of the nucleons involved change?
DOWN quark to UP quark.
what force is involved in electromagnetic repulsion?
electromagnetic force.
what force is involved in beta minus decay?
weak nuclear force.
describe what happens to the participants of beta plus decay?
PROTON –> NEUTRON.
emits a BETA PLUS particle (e+) + ELECTRON NEUTRINO.
what is the exchange particle of electromagnetic repulsion?
virtual photon.
what is the exchange particle for beta minus decay?
W- boson.
what is the exchange particle for beta plus decay?
W+ boson.
what force is involved with beta plus decay?
weak nuclear force.
what particles are involved with electron capture?
PROTON interacts with ELECTRON.
–> NEUTRON + ELECTRON NEUTRINO.
what particle interactions are similar? what is the difference between them?
electron capture and proton-electron collision. difference is proton-electron collision take places at VERY HIGH SPEEDS.
what is the exchange particle for electron capture?
W+ boson.
what particles are involved in proton-electron collision?
PROTON collides with ELECTRON (at HIGH SPEEDS ++) –> NEUTRON + ELECTRON NEUTRINO.
what is the exchange particle for proton-electron collision?
W- boson.
** what particles are involved in neutron and neutrino interaction? **
neutron + neutrino –> proton + beta minus.
**what is the exchange particle for neutron and neutrino interaction? **
W- boson.
what particles are formed when a proton and an antineutrino interact?
proton + antineutrino –> neutron + positron.
what is the exchange particle for the proton - antineutrino interaction?
W+
what is another name for a beta minus particle?
electron.
after annihilation occurs, why do the photons produce move off in opposite directions?
to conserve linear momentum.
how many photons are required to pair produce?
ONE.
definition of an eV?
equal to the KE gained by an e- when accelerated by a PD of 1V.
rest energy equation?
E = mc^2
describe what happens when a positron and its antiparticle meet? (2 marks)
positron and electron annihilate, producing x2 photons of equal energy (that move off in opposite directions).
why do a particle and its antiparticle move off in opposite directions after pair production?
the have opposite charges.
what is the fundamental force responsible for proton-electron collision?
weak nuclear force (weak interaction).
state why the total energy after the annihilation collision is greater than the KE before the collision.
total energy must include KE and rest energy.
do photons have rest mass?
no.
how does the nucleon composition of the nucleus change after beta minus decay?
number of protons decreases increases by ONE.
nucleon number remains the same.
how does the nucleon composition of the nucleus change after beta minus decay?
number of protons decreases by ONE.
nucleon number does not change.
what is 1MeV equal to?
1 x 10^6 eV.
power of the laser beam equation?
power = n x h x f.
n: no. photons passing a fixed point each second.
order the pion, muon and kaon from largest to smallest rest mass.
kaon, pion, muon.
what is the charge of an up quark? why does it have this charge?
+2/3.
a baryon is made up of three quarks. baryon charge is +1/-1/0 (integer), quark composition makes up total charge.
what is the charge of a down quark? why does it have this charge?
-1/3.
a baryon is made up of three quarks. baryon charge is an integer, charges of quark composition make up total charge.
what is the quark combination of a neutron?
udd
what is the quark composition of a proton?
uud.
show that charge is conserved in beta decay.
udd -> uud + e- + (anti) Ve.
+2/3 + (-1/3) + (-1/3) –> + 2/3 +2/3 + (-1/3) + (-1)
why are protons and kaons in different categories of particles?
protons are made of 3 quarks whereas kaons are made of a quark and its anti-quark.
what are the two subgroups of hadrons? give examples of s.a particles in each group.
baryons: proton/neutron.
mesons: electron/pion/kaon.
how are leptons different to hadrons?
leptons do not interact via the strong force whereas hadrons interact by all fundamental forces. leptons are fundamental particles so cannot be broken down whereas hadrons can.
what are the five aspects of a decay equation that must be conserved?
baryon number; lepton (e-) number; lepton (muon) number; charge; momentum.
why must lepton (e-) number and lepton (muon) number be counted separately?
muons cannot decay into electrons or electron neutrinos (and vise versa) so decay equation may obey lepton conservation but may not be possible.
how do the rules regarding the conservation of strangeness change for weak vs strong interaction?
strangeness is always conserved in the strong interaction. strangeness can change in the weak interaction.
are protons involved in meson decay?
no, only baryon decay.
true/false: a baryon number is always an integer.
true.
where can mesons be found?
cosmic rays; particle accelerators.
is a muon a lepton or a meson?
lepton - it is a fundamental particle so cannot be broken down into quarks.
true/false: up, down and strange quarks have the same baryon number?
true.
what is the baryon number of an up quark?
+1/3.
what changes about baryon number, lepton number, charge and strangeness in a corresponding antiparticle.
change in sign - (+)ve to (-)ve and vise versa.
give one characteristic of a strange particle that makes it different from a non strange particle.
(1 mark)
contains a strange quark.
longer half life than expected.
decays via weak interaction.
what proves that light is not a wave?
max. kinetic energy did not increase with intensity.
changing intensity had no effect below the threshold frequency.
