Physics - Standard Model
OCR A-Level Physics 2022
Flashcards
The four fundamental forces
What are the four fundamental forces?
- Strong nuclear force
- Weak nuclear force
- Electromagnetic force
- Gravitational force
In what context does the strong nuclear force show up?
Holding nucleons together.
When does the electromagnetic force act?
When two charged objects interact.
Relative strengths of the forces
What is the relative strength of the electromagnetic force?
What is the relative strength of the gravitational force?
Ranges of the forces
Strong force attraction and repulsion
When is the strong nuclear force attractive?
Between $3 \text{fm}$ and $0.5\text{fm}$.
When is the strong nuclear force repulsive?
At distances less than $0.5\text{fm}$.
Antiparticles
What, according to the Standard Model, comes with every type of particle?
A corresponding antiparticle.
What two things are true about a particle’s corresponding antiparticle?
- Same mass
- Opposite charge
What, in terms of quarks, are the antiparticle versions of hadrons made from?
Antiquarks.
Fundamental particles
What is a fundamental particle?
A particle that has no internal structure and so cannot be divided into smaller particles.
What is the process where a particle and an antiparticle are mutually destroyed called?
Annihilation.
Why isn’t a proton or a neutron a fundamental particle?
Because they can be divided into quarks.
Leptons and hadrons
What are the two broad categories of particles in the standard model?
- Leptons
- Hadrons
How can you remember that hadrons have mass?
Think “the large hadron collider”, it has to shove things with mass into one another.
What is a lepton?
A fundamental particle that does not experience the strong nuclear force.
What is a hadron?
A non-fundamental particle that do experience the strong nuclear force and decay via the weak nuclear force.
Baryons and mesons
In terms of the sub-categories of hadrons, what is most of ordinary matter made from?
Baryons.
In terms of the sub-categories of hadrons, which consist of three quarks?
Baryons.
In terms of the sub-categories of hadrons, which consist of quark-antiquark pair?
Mesons.
What is true about the quark-antiquark pair in a meson?
The quarks are not of the same type, otherwise they’d annihilate one another.
The six quarks
Quark composition of particles
How can you work out the overall charge of a particle from its quarks?
Add them together.
What combination of quarks makes an electron?
Trick question – electrons are not made of quarks.