24 - Particle Physics Flashcards
Describe the alpha particle scattering experiment.
- Alpha particles fired at gold foil
- Scattered through 180 degrees
- Detected on fluorescent sphere by microscope
What were the observations from the alpha particle experiment?
- Most particles were not scattered
- Only a very tiny amount were scattered more than 90 degrees
What can we learn about an atom from the alpha particle scattering experiment?
- Most of an atom is empty space with dense mass at centre
- Nucleus is positively charged
What is the average order of magnitude of the radius of a nucleus?
10⁻¹⁵
What is the average order of magnitude of the radius of an atom?
10⁻¹⁰
What is a nucleon?
A proton or a neutron
What is the nucleon number?
number of protons and neutrons in the nucleus
What is the top number (A) of a chemical notation?
Nucleon number
What is the bottom number (Z) of a chemical notation?
Proton number
How do we calculate the mass of an atom / nucleus?
Nucleon number x relative atomic mass (u)
What does u stand for?
Relative atomic mass.
What is the order of magnitude of density of a nucleus?
10¹⁷
What is the order of magnitude of density of an atom?
10³
Why must the strong nuclear force exist?
Because if it didn’t, the electrostatic repulsion between protons wouldn’t allow nuclei to exist.
Describe the nature of the strong nuclear force.
- Acts over a very small range
- Repulsive up to 0.5 fm
- Attractive between 0.5 and 3 fm
What is the order of magnitude of a fm?
10⁻¹⁵m
What is an antiparticle?
A particle with the same rest mass as its particle version but the opposite charge.
What happens when a particle and an antiparticle collide?
They annihilate.
How do we symbolise an anti particle?
With a bar above the symbol.
Rank the fundamental forces in order of strength.
(weakest to strongest).
Gravitational
Weak nuclear
Electromagnetic
Strong nuclear
What is a fundamental particle?
A particle with no internal structure - it cannot be further divided
What is a hadron?
A particle which is affected by the strong nuclear, weak nuclear and electromagnetic forces.
Made of quarks.
Give three examples of hadrons.
Protons
Neutrons
Mesons
What is a lepton?
A particle not affected by the strong nuclear force but affected by the weak nuclear and electromagnetic forces.
