Chapter 24 - Particle Physics Flashcards
What was Rutherford’s alpha-scattering experiment?
Beam of alpha particles targeted at thin piece of gold foil, they were scattered and detected on a screen.
Observations and conclusions made from the gold foil experiment.
- Most alpha particles passed straight through - most of the atom is empty space, mass concentrated in small region.
- Very few alpha particles were deflected by more that 90 degrees - nucleus has positive charge.
What is the radius of the nucleus?
10 to the -15 m.
What is the radius of the atom?
10 to the -10 m.
What is an isotope?
Nuclei of the same element that has the same number of protons but different number of neutrons.
Describe the nature of the strong nuclear force.
Holds nucleus together.
Short range - Attractive to about 3 fm and repulsive below about 0.5 fm.
What happens when a particle meets its antiparticle?
They annihilate each other and release energy in the form of high energy pair of photons.
Fundamental particle
Has no internal structure therefore cannot be split into smaller particles.
Quarks, electrons and neutrinos.
What are the categories of subatomic particles?
Hadrons - affected by the strong nuclear force e.g. protons, neutrons, mesons.
Leptons - not affected by strong nuclear force e.g. electrons, neutrinos, muons.
Both experience electromagnetic force if charged.
State the quark composition of a proton.
uud
State the quark composition of a neutron.
udd
Charge on up quark.
+ 2/3
Charge on down quark.
- 1/3
Charge on strange quark.
- 1/3
What is a meson?
Hadron made up of a quark and anti-quark.
