24 - Particle Physics Flashcards
Thomsons model for atom
Plum pudding model:
atom is a positively charged sphere with negatively charged electrons embedded within
Observations and conclusions of Rutherfords alpha scattering experiment
most alpha particles passed straight through showing most of the atom is empty space
some were deflected showing that the nucleus is a dense mass concentrated in the centre
some deflected with angles larger than 90º showing that the nucleus had to be a positive charge
size of atom and nucleus
radius of nucleus is about 10^-14m and radius of atom is about 10^-10m (nucleus is about 10^5 smaller than the atom)
how to prove proportionality
prove that value of k is the same (constant) for each result
nucleon refers to
a proton or neutron
A represents
nucleon number
Z represents
proton number
isotopes are
nuclei of the same element with same number of protons but different number of neutrons
what is one atomic mass unit
one twelfth the mass of a carbon-12 atom
mass in atomic mass units equation
m=Au
mass = nucleon number x u
nuclear size density equation
R=r0 x A^1/3
radius of nucleus = r0 x nucleon number^1/3
assumptions for density and volume
nucleons are packed together with little to or no empty space
force holding nucleus together and why needed
strong nuclear force as grav force attracting nucleons is not enough to match the electrostatic force repelling nucleons
negative force is an
attractive force
nature of strong nuclear force
can be attractive and repulsive
has a short range
affects all nucleons
attractive to 3fm and repulsive below 0.5fm (graph)
nature of electrostatic force
repulsive force
long range
nature of gravitational force
attractive force
long range
what are fundamental particles
particles that cant be divided into smaller parts (no internal structure)
e.g. quarks, electrons, neutrinos
antimatter
every particle has its corresponding antiparticle which has the same mass but opposite charge (antiparticle represented by bar over letter).
when they meet, they destroy each other in a process called annihilation - mass of particles are turned into pair of high energy photons - cosmic rays
antiparticle for electron
positron e+
fundamental forces in order of strength
strong nuclear, electromagnetic, weak nuclear, gravitational
fundamental forces - ranges
grav and EM - infinite
strong nuclear - 10^-15m
weak nuclear - 10^-18m
first categorisation of sub atomic particles
HADRONS AND LEPTONS
hadrons
affected by SNF
e.g. protons neutrons mesons (and antiparticles)
if charged experience EM force
decay with WNF
