Particles and medical physics: Particle Physics Flashcards
Describe the set up of Rutherford’s alpha-scattering experiment
alpha particles (Helium 4 nuclei) were fired at thin sheet of gold and were scattered by the spaces between the lattice and were detected on a fluorescent screen.
What were the observations on the Rutherford alpha-scattering experiment
1999/2000 alpha-particles go through the lattice undeflected: meaning the atom is nearly all empty space
1/2000 alpha particles are deflected: implying a dense nucleus
1/10000 are scattered by angles greater than 90° which was found out to imply that the nucleus is positively charged as it repels the positively charges alpha particle
describe how to estimate the size of a nucleus using an energy approach
positive when a negatively charged particle is accelerated towards a nucleus with initial KE K there is a point in space in which initial KE = the electric potential energy at a distance d.
KE = Qq/4πε0d where Q is the charge on the nucleus and q = the charge of the incident particle
what is the approximate size of an Atom
1x10^-10 or 1Å
What 2 particles are found in a nucleus and what are they sometimes referred to as
Protons/ Nutrons, Nucleons
what is the charge on a proton, neutron and electron
+e,0,-e or +1.6x^-19,0,-1.6x^-19
what is a neutral atom?
same number of electrons and protons
define an isotope
an atom with the same number of protons but a differing number of neutrons
how is the unified atomic mass unit defined and what is its vaule
1/12 the mass of a neutral Carbon-12 atom
1.661x10^-27 kg
what is the approximate radius of a nucleus
1x10^-15 m
Describe the equation used to determine the radius of the atom
R=r0A^1/3 where R is the radius of the atom where r0 is the radius of a proton and A is the nucleon number
describe the ranges in which the strong nuclear force acts over and how it varies
Acts over the range from (0,3]fm for distances <0.5fm the force is repulsive
1.5fm is the maximum
stops acting at distances x>3fm
what are the 4 fundamental forces
strong nuclear
electromagnetic
weak nuclear
gravitational
what are the 2 families of fermions
hadrons and leptons
what are the 2 types of hadrons
Mesons and Baryons
how is a baryon identified
a baryon has a 3 quark composition e.g, a proton or neutron
how is a meson identified
a meson is comprised of a quark, antiquark pair
what is a lepton
fundamental particles not composed of quarks e.g. a electron or neutrino
what are the 6 types of quark
up, down, bottom, top, strange, quark
what are the 6 types of antiquark
anti-up, anti-down, anti-bottom, anti-top, anti-strange, antiquark
what is the charge on an up quark
+2/3 e
what is the charge on an anti-up quark
-2/3 e
what is the charge on a down quark
-1/3 e
what is the charge on a anti-down quark
+1/3 e
what is the charge on a bottom quark
-1/3e
what is the charge on a anti-bottom quark
+1/3e
what is the charge on a top quark
+2/3e
what is the charge on a anti-top quark
-2/3e
what is the charge on a charm quark
+2/3 e
what is the charge on an anti-charm quark
-2/3 e
what is the charge on a strange quark
-1/3 e
what is the charge on an anti-strange quark
+1/3 e
what is the quark composition of a proton
u,u,d
what is the quark composition of a neutron
udd
what is the equation for β+ decay
proton -> neutron + positron + electron neutrino
what is the equation for β- decay
neutron -> proton + electron + antielectron neutrino
in β- decay, what is the equation for the quark changes
d -> u + electron + antielectron neutrino
in β+ decay, what is the equation for the quark changes
u ->d + positron + electron neutrino
what 3 things are conserved in a decay equation
charge
lepton number
baryon number
