Section 1- Particles

Question 1

What is specific charge?

Answer 1

The charge to mass ratio
charge/mass
C/kg

Question 2

What is the relative mass of an electron?

Answer 2

0.0005

Question 3

What letter is associated with a proton number?

Answer 3

Z

Question 4

What is a nucleon?

Answer 4

A constituent of the nucleus - a proton or a neutron

Question 5

What letter represents the nucleon number?

Answer 5

A

Question 6

What is an isotope?

Answer 6

A version of an element with the same number of protons but a different number of neutrons

Question 7

What is a use of radioactive isotopes?

Answer 7

Carbon dating - the proportion of carbon-14 in a material can be used to estimate its age

Question 8

What is the strong nuclear force?

Answer 8

The fundamental force that keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons

Question 9

Describe the range of the strong force

Answer 9

• Repulsive - up to 0.5fm
• Attractive - from 0.5-3fm
• Negligible past 3fm

Question 10

What makes a nucleus unstable?

Answer 10

Nuclei which have too many of either protons or neutrons or both

Question 11

How do nuclei with too many nucleons decay?

Answer 11

Alpha decay - emission of a helium nucleus

Question 12

How do nuclei with too many neutrons decay?

Answer 12

Beta minus decay - the neutron decays into a proton by the weak interaction and releases an electron and an anti-electron neutrino with the W- exchange particle

Question 13

How was the existence of the neutrino hypothesised?

Answer 13

The energy of particles after beta decay was lower than before, a particle with 0 charge (to conserve charge) and negligible mass must carry away this excess energy

Question 14

What is an alpha particle?

Answer 14

A particle that contains 2 protons and 2 neutrons, the same as a helium nuceus

Question 15

What is an anti-particle

Answer 15

For each particle there is a corresponding anti-particle with the same rest energy and mass but all other properties are the opposite of its respective particle

Question 16

What is the name of the anti-particle of an electron?

Answer 16

Positron

Question 17

What is the anti-particle of a π0 (pion with 0 charge)?

Answer 17

π0 - its anti-particle is itself

Question 18

What occurs when a particle and antiparticle meet?

Answer 18

Annihilation - the mass of the particle and antiparticle is converted back to energy in the form of 2 gamma ray photons which go in opposite directions to conserve momentum

Question 19

What is pair production?

Answer 19

A gamma ray photon is converted into a particle-antiparticle pair

Question 20

What is the minimum energy of a photon required to make a particle-anti-particle pair?

Answer 20

2 x rest energy of the particle

Question 21

What are the 4 fundamental forces?

Answer 21

1. Gravity
2. Electromagnetic
3. Weak nuclear
4. Strong nuclear

Question 22

The virtual photon is the exchange particle of which force?

Answer 22

The electromagnetic force

Question 23

What type of particles are affected by the strong nuclear force?

Answer 23

Hadrons

Question 24

What is the exchange particle of the weak nuclear force?

Answer 24

The W boson - W+ or W-

Question 25

What does the electromagnetic force act on?

Answer 25

Charged objects

Question 26

When does weak nuclear interaction occur?

Answer 26

When quark character changes (a quark changes into another quark), it affects all types of particles

Question 27

What properties must be conserved in particle interactions?

Answer 27

* Energy * Charge * Baryon number * Lepton number * Momentum * Strangeness (only for strong interactions)

Question 28

Why do we need ensure strangeness is conserved in the strong interaction?

Answer 28

The quantum number reflects the fact that strange particles are always created in pairs

Question 29

How can strangeness change in the weak interaction?

Answer 29

By 0, +1 or -1

Question 30

What is a hadron?

Answer 30

* Baryons and mesons * Made of 2 or more quarks held together by the strong nuclear force

Question 31

What are the classes of hadrons?

Answer 31

* Baryons (3 quarks) * Mesons (1 quark, 1 anti-quark)

Question 32

The pion and kaon are both examples of which class of particle?

Answer 32

Mesons

Question 33

What are the quark structures of pions and kaons?

Answer 33

π+ - ud¯ π− - du¯ π0 - u¯u or d¯d K+ - us¯ K- - su¯

Question 34

The pion can be an exchange particle for which force?

Answer 34

The strong nuclear force

Question 35

What particle does a kaon decay into? Give 2 decay equations for this

Answer 35

A kaon always decays into a pion K+ -> π+ + π0 or K+ -> π+ + π+ + π-

Question 36

Give some examples of baryons and their quark structures

Answer 36

* Protons - udu * Neutrons - dud

Question 37

What is significant about a proton?

Answer 37

* It is the only stable baryon * All baryons will eventually deacy into protons

Question 38

What are some examples of leptons?

Answer 38

* Electron * Muon * Neutrino * Anti-particles of the above

Question 39

What does a muon decay into?

Answer 39

An electron, an electron neutrino and a muon neutrino

Question 40

What is the strangeness value of a strange quark?

Answer 40

-1

Question 41

What are strange particles?

Answer 41

Particles that are produced through the strong interaction and decay through the weak interaction

Question 42

What is the equation for electron capture?

Answer 42

p + e- -> n + Ve

Question 43

How can you detect electrons?

Answer 43

Use a cloud emission chamber