chapter 24 - Particle physics Flashcards
What type of particles were used in Rutherford’s scattering experiment?
Alpha particles
What power of 10 is the diameter of a nucleus?
10^-15m
What power of 10 is the diameter of an atom?
10⁻¹⁰m
What material was used as a target in Rutherford’s scattering experiment?
Gold foil, a few atoms thick
What was measured in Rutherford’s scattering experiment?
The angle of deflection of the alpha particles.
What happened to most of the alpha particles in Rutherford’s scattering experiment?
They passed straight through the foil (with very little scattering).
What proportion of alpha particles were scattered in Rutherford’s scattering experiment?
Around 1 in 2000
What proportion of alpha particles were deflected by more than 90° in Rutherford’s scattering experiment?
Around 1 in 10,000
What was concluded due to most of the alpha particles passing straight through the gold foil Rutherford’s scattering experiment?
Most of the atom is empty space with most of the mass concentrated in a small nucleus.
What was concluded due to some alpha particles being scattered in Rutherford’s scattering experiment?
The nucleus is positively charged.
How did Rutherford estimate the maximum radius of the nucleus?
He equated the KE of the alpha particle to the electric potential energy at closest approach to the nucleus.
What is a nucleon?
A proton or neutron.
What is an atomic mass unit?
One twelfth of the mass of a neutral carbon 12 atom.
How has the radius of the nucleus been measured?
By the diffraction of fast moving electrons.
What is R in R = r₀A^(1/3)?
The radius of the nucleus.
What is r₀ in R = r₀A^(1/3) roughly equivalent to?
The radius of a proton.
What is A in R = r₀A^(1/3)
Nucleon number.
What force holds protons and neutrons together in the nucleus?
The strong nuclear force.
What is the maximum range of the strong nuclear force?
~3fm
Below what distance is the strong nuclear force repulsive?
0.5fm
Which group of particles are subject to the weak nuclear force but not the strong nuclear force?
Leptons
What is the quark composition of a meson?
One quark and one antiquark
Which force do Hadrons decay by?
The weak nuclear force.
What is the quark composition of a Baryon
Three quarks
What is a neutrino?
A lepton with no charge and a tiny mass.
Why doesn’t a neutrino experience the electromagnetic force?
They have no charge..
What is the quark composition of a neutron?
up down down (udd)
What is the quark composition of a proton?
up up down (uud)
What is the quark composition of an anti-baryon?
Three antiquarks
Name the two types of hadron.
baryons and mesons
What force hold quarks together in hadrons?
The strong nuclear force.
What is the family of particles that are subject to both the strong and weak nuclear force?
Hadrons
What type of particle are nucleons?
Baryons
How does a proton compare to an antiproton?
The have the same mass but opposite charge.
How does an electron compare to a positron?
The have the same mass but opposite charge.
What is the antiparticle of the electron?
Positron.
What type of particle are there millions of passing through your body every second?
Neutrinos
Describe beta minus decay.
A neutron in an unstable nucleus decays into a proton
Describe beta plus decay.
A proton in an unstable nucleus decays into a neutron
What quark transformation occurs during beta minus decay?
A down quark (in a neutron) turns into an up quark (in a proton)
What quark transformation occurs during beta plus decay
An up quark (in a proton) turns into an down quark (in a neutron)
