3.2 Particles and Radiation Flashcards
Charge of proton / electron?
1.6x10^-19 C/ -1.6x10^-19 C
relative mass of electron?
0.0005
What does A represent?
nucleon number
What does Z represent?
proton number
What is an isotope?
Same number of protons (same element) but diff number of neutrons
What can isotopes be used for?
carbon dating, medicine, nuclear fission
What is carbon dating?
All living things have the same ratio of carbon14 to carbon12
When an organism dies, the (radioactive) carbon14 decays.
Physicists use the percentage of carbon14 left and compare it with isotopic data to calculate the age
What are the four fundamental forces?
gravity, electromagnetic, strong nuclear, weak nuclear
where is the strong force repulsive?
below 0.5fm (to stop the nucleus from collapsing in on itself)
Where is the strong nuclear force attractive?
between 0.5-3 fm; negligible up to 5fm when overtaken by electrostatic force
What is a beta-minus particle?
a fast-moving electron emitted by radioactive decays
What very small particle is emitted in beta-decay?
a neutrino
EM radiation is made of WHICH particles of light with WHAT energy (equation)?
Photons
E=hf
What is annihilation?
When a particle and its anti-particle meet and all the mass gets converted into energy in the form of two gamma photons
What is pair production?
A photon turns into a particle-antiparticle pair. The energy gets converted unto mass: the minimum energy for the photon to do this must be at least the total rest mass of the two particles produced.
What does the electromagnetic force affect and what is the exchange particle?
all charged particles / virtual photons
What does the weak nuclear force affect and what are the exchange particles?
all particles / W+, W- bosons
What does gravity affect and what are the exchange particles?
all particles / graviton
What direction is time in Feynman diagrams?
up
Describe the electromagnetic repulsion Feynman diagram
two electrons in, two electrons out, virtual photon between them
Describe the Feynman diagram for beta plus decay
proton turns to a neutron, positron, and electron neutrino; has a W+ boson in between neutron and other two products
Describe the Feynman diagram for beta minus decay
neutron turns to a proton, electron, and anti-electron neutrino; W- boson between proton and other two products
Describe the Feynman diagram for electron capture
proton and electron in, W+ boson between (electron direction), neutron and electron neutrino out
What are the two types of hadrons
baryons and mesons
Which particles does the strong nuclear force affect and what is the exchange particle/
hadrons / pions + gluons
leptons do not interact with which force?
the strong nuclear force
what are the four leptons?
electrons, muons, electron neutrino, muon neutrino
What class of particles do quarks make up?
hadrons - baryons and mesons
what is the quark composition of a proton?
up, up, down
what is the quark composition of a neutron?
up, down, down
what is the quark composition of an antineutron?
anti-down, anti-down, anti-up
what is the quark composition of an antiproton?
anti-up, anti-up, anti-down
what is the strangeness of a strange quark?
-1
what is the strangeness of an anti-strange quark?
1
What is the weak nuclear force responsible for?
decay
Why may carbon dating not be reliable in the future?
Due to burning fossil fuels and open-air bomb testing, the ratio of different carbon isotopes will be altered (human activity)
what are the uses of carbon dating?
finding the age of different fossils
information on the changes in climate
What are the three different hydrogen isotopes?
PROTIUM - 1 proton, 99.98% of Hydrogen atoms, used in Hydrogen fuel cells
DEUTERIUM - 1 proton+1 neutron, used in nuclear fusion
TRITIUM - 1 proton+2 neutrons, used is thermonuclear fusion weapons
Describe alpha decay
2protons+2 neutrons released, for very large nuclei, proton number = -2, nucleon number = -4
how was the (anti)neutrino theorised?
The kinetic energy graph shows that beta particles have a range of kinetic energies. There is a fixed amount of energy so there must be another particle (neutrino) which carries away that missing energy; accounts for conservation of energy in beta-minus decay
What is the rule for mass/ energy in pair production?
the energy of the photon must be at least equal to the rest mass of the particle-antiparticle pair created
which waves have the highest/ lowest frequencies?
gamma has highest frequency + energy
radio has the lowest frequency + energy
What is the difference between an emission spectrum and an absorption spectrum?
Photons are energy carriers; in absorption, the atom moves up energy levels by absorbing a photon, and in emission the atom moves down energy levels by emitting a photon.
How do fluorescent tubes work?
High voltage applied to mercury vapour in tubes, which accelerates free electrons, ionising mercury atoms to excite their electrons. When they de-excite, they emit UV photons. Phosphor coating on inside of tubes absorb UV photons, which excites its electrons. When these de-excite, they emit visible light photons
Which colours have the highest/ lowest wavelengths?
Red has highest (700 nm) and violet has lowest (380 nm)
Where are strange particles produced/ decay?
Produced in strong interaction
Decay in weak interaction
Explain which of the four fundamental forces is responsible for the decay of the neutron
The weak nuclear force which includes a change in quark structure
Explain how electron paths change due to forces between two of them
They experience the electromagnetic force, carried out by a virtual photon, which has momentum. The principle of conservation of momentum enables the electron path to change
Why is progress in (particle) Physics slow?
It requires international collaboration and verification
Investment in expensive is needed
