Particles

Question 1

What is specific charge?

Answer 1

Ratio of electric charge to mass

Question 2

What is a nuclide?

Answer 2

A distinct kind of atom or nucleus characterised by a specific number of protons and neutrons

Question 3

What is an isotope?

Answer 3

An atom of an element with a different number of neutrons

Question 4

What is a nucleon?

Answer 4

A proton or neutron

Question 5

What are the 4 fundamental forces?

Answer 5

• Gravitational
• Electromagnetic
• Strong
• Weak

Question 6

At what ranges does the strong force have a strong attractive force?

Answer 6

Between about 0.5 fm and 3 fm

Question 7

What is an alpha particle?

Answer 7

2 protons and 2 neutrons / Helium nucleus

Question 8

What is the different between accelerating electrons and electrons orbiting an atom?

Answer 8

Accelerating electrons release photons whereas orbiting electrons do not

Question 9

What is a beta particle?

Answer 9

Fast-moving, ejected electrons created in neutron decay

Question 10

What is gamma radiation?

Answer 10

Electron magnetic radiation that accompanies other forms of radiation.

Question 11

What is the main “purpose” of gamma radiation?

Answer 11

To get rid of excess energy

Question 12

What happens when matter and antimatter meet?

Answer 12

They annihilate each other and release all their energy as radition.

Question 13

Describe Positron Emission Tomography (PET)

Answer 13

• Positron enters the bloodstream and then almost immediately meets an electron, producing 2 gamma rays
• These are detected by sensors and gradually an image is formed

Question 14

What did Dirac’s theory predict about antiparticles?

Answer 14

• For each particle there is a corresponding antiparticle
• Annihilates both particles, converting their total mass into photons
• Has exactly the same rest mass
• Has exactly the opposite quantum properties (charge, lepton number, baryon number)

Question 15

What is annihilation?

Answer 15

When a particle and antiparticle meet their rest mass energy is converted into two high energy photons.

Question 16

Why are two photons produced in annihilation?

Answer 16

So that momentum is conserved

Question 17

What is pair production?

Answer 17

When a photon with sufficient energy passes nearby a particle with mass, a new particle and corresponding antiparticle are created.

Question 18

How does the minimum photon energy compare in annihilation and pair production?

Answer 18

E_{Pair Production} = 2E_Annihilation

Question 19

What are Feynman Diagrams?

Answer 19

Diagrams that illustrate particle interactions and can be used to predict other interactions

Question 20

What are the rules in a Feynman diagram?

Answer 20

• Quantum quantities are conserved at verticies
• Straight lines represent particles
• Wiggly lines represent virtual particles

Question 21

What are force carriers?

Answer 21

• They transfer force in a field
• Include: photon, W boson, pion

Question 22

What is the weak interaction?

Answer 22

Responsible for decay and has the W boson as the exchange particle.

Question 23

What are properties of the W boson?

Answer 23

• Have non-zero mass
• Very short range (0.001fm)
• Carry charge

Question 24

What is electron capture?

Answer 24

A proton in a proton-rich nucleus turns into a neutron and neutrino as a result of interacting through the weak force with an inner-shell electron

Question 25

What is an electron-proton collision?

Answer 25

If an electron and proton are accelerated and collided at high speeds, an interaction similar to electron capture will occur but instead a W^- boson is emitted

Question 26

What are cosmic rays?

Answer 26

- High energy particles that travel through space from stars - Fast moving protons or small nuclei

Question 27

What happens when cosmic rays enter the atmosphere?

Answer 27

They collide with gas atoms and create new short-lived particles

Question 28

What are the properties of the muon?

Answer 28

- Negatively charged - Rest mass 200 times the rest mass of the electon

Question 29

What are the properties of pions?

Answer 29

- Can be positively charged (π⁺), negatively charged (π^-) or neutral (π⁰) - Rest mass: µ < π < p

Question 30

What are the properties of kaons?

Answer 30

- Can be positively charged (K⁺), negatively charged (K^-) or neutral (K⁰) - Rest mass: π < K < p - Strange particle

Question 31

What are the properties of strange particles?

Answer 31

- Contain a strange quark or antiquark - Have surprisingly long lives - Created in pairs by the strong interaction - Decay by the weak interaction

Question 32

Is strangeness conserved in the strong interaction?

Answer 32

Yes

Question 33

Is strangeness conserved in the weak interaction?

Answer 33

No

Question 34

What is a hadron?

Answer 34

Particles and antiparticles that can interact through the strong interaction

Question 35

What is a lepton?

Answer 35

Particles and antiparticles that cannot interact through the strong interaction

Question 36

What are the different types of hadrons?

Answer 36

- Baryons - Mesons

Question 37

What are baryons?

Answer 37

Protons and all other hadrons that have protons in their decay products. Made up of 3 quarks or antiquarks.

Question 38

What are mesons?

Answer 38

Hadrons that do not contain protons in their decay products. Made of a quark, antiquark pair.

Question 39

What are the different leptons?

Answer 39

- electron - muon - neutrino

Question 40

What are the different baryons?

Answer 40

- proton - neutron

Question 41

What are the different mesons?

Answer 41

- pion - kaon