Particle Physics Flashcards
Describe Rutherfords alpha scattering experiment
A beam of alpha particles, each with the same kinetic energy, was fired at a thin gold foil causing them to scatter. The scattered alpha particles were detected by a zinc sulfide screen, producing tiny specks of light visible through a microscope. The microscope was moved to measure the number of alpha particles scattered at different angles, ranging from 0° to nearly 180°.
What is the plum pudding model
A neutral atom is made up of a uniform sphere of positive charge with tiny electrons embedded in it.
What were the observations and conclusions of the alpha scattering experiment
Most particles passed through the gold foil with little scattering, which means that most of the atom is empty space with the majority if its mass is concentrated in a small region called the nucleus.
Few particles where scattered by more than 90 degrees, which means that the nucleus was positively charged as it repelled the positive alpha particles that came near it.
How is the nucleus of an atom represented
A/Z next to X, where A is the total amount of nucleons in the nucleus, Z is the amount of protons and X is the element
What are isotopes
Isotopes are nuclei of the same element that has the same number of protons but different amount of neutrons
What is one atomic mass unit
1.661 x 10^-27kg
How do you calculate the radius of a nucleus
Radius = 1.2 x 10^-15 x nucleon number ^ 1/3. R = r0xA^1/3
What is the strong nuclear force
The attractive force between nucleons and quarks that is effective between 3 and 0.5 femtometres
What is antiparticle
Antiparticles have the same mass as particles of ordinary matter but opposite charges and quantum properties. When a particle and its antiparticle meet, they annihilate each other and their masses are converted into a pair of high energy photons.
What are the fundamental forces
Strong Nuclear - Relative strength: 1 - Range: -10^-15
Weak Nuclear - Relative strength: 10^-6 - Range: -10^-18
Electromagnetic - Relative strength 10^-3 Range: Infinite
Gravitational - Relative strength: 10^-40 Range: Infinite
What are hadrons
Particles and antiparticles that contain quarks. Are affected by the strong nuclear force. If they are charged they experience electromagnetic forces. Decay by weak nuclear forces.
What are leptons
Fundamental particle. Particles or antiparticles not affected by strong nuclear forces. If charged, experience electromagnetic forces.
What are quarks
Fundamental particles that are the building blocks of all hadrons.
Describe the Up, down and strange quarks
Up quark has a charge of 2/3, Down quark has a charge of -1/3, and strange quarks have a charge of -1/3. Anti up, down and strange quarks have opposite charges and are denoted with a bar over their letter.
What are the quarks within a proton and nuetron
up, up down, and down down up.
What are baryons
Hadrons with any 3 combinations of quarks
What are mesons
Hadrons with a quark and antiquark
What is a neutrino
Fundamental particles with no charge. Electron neutrino and electron anti neutrino are released in beta decay.
What are the different beta decays
Alpha radiation is the emission of helium nuclei. Beta radiation is the emission of electrons or positrons and gamma radiation is the emission of high energy gamma photons.
What happens in a beta minus decay
Due to weak nuclear forces, a neutron in an unstable nucleus decays into a proton, electron and electron antineutrino. One down quark becomes an Up quark. Total charge is conserved
What happens in beta plus decay
Due to weak nuclear forces, a proton in an unstable nucleus decays into a neutron, anti electron and electron neutrino. One Up quark becomes a down quark. Total charge is conserved.
