2.1 Particles

Question 1

What is meant by Specific Charge?

Answer 1

The Charge to Mass ratio:
Specific Charge = charge/mass
Units: C/kg

Question 2

What is Nucleon?

Answer 2

A constituent of the nucleus : proton or neutron

Question 3

What is an isotope?

Answer 3

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

Question 4

State a use of radioactive isotopes.

Answer 4

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

Question 5

What is the strong nuclear?

Answer 5

the fundamental force that keeps the nucleus stable by counteracting the electrostatic repulsive force between protons

Question 6

Describe the range of the strong force.

Answer 6

1) repulsive up to 0.5fm
2) attractive from 0.5-3fm
3) negligible past 3fm

Question 7

What makes a nucleus unstable?

Answer 7

Nuclei with either too many of either protons or neutrons

Question 8

How do nuclei with too may nucleons decay?

Answer 8

Alpha decay (emissions of helium nucleus - 2 protons and 2 neutrons)

Question 9

How do nuclei with too many neutrons decay?

Answer 9

Beta minus decay in which the neutron decays into a proton b the weak interaction (quark character has changed from udd to uud )

Question 10

How was the existence of the neutrino hypothesised?

Answer 10

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

Question 11

What is meant by beta minus decay?

Answer 11

When a neutron turns into proton , the atom releases an electron and an anti-electron neutrino

Question 12

What is an anti particle?

Answer 12

For each particle there is an anti particle , they have the same rest energy and mass , but everything else is opposite so they have the opposite charge

Question 13

What occurs when a particle and an anti-particle meet?

Answer 13

Annihilation:
The mass of the particle and anti-particle is converted into energy in the form of 2 gamma ray photons going in opposite directions to conserve momentum

Question 14

What is pair production?

Answer 14

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

Question 15

What is the minimum energy of a photon needed to make a proton antiproton pair?

Answer 15

2x proton rest energy

Unit:eV

Question 16

Name the 4 fundamental forces?

Answer 16

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

Question 17

The virtual photon is the exchange particle between what force?

Answer 17

The electromagnetic force

Question 18

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

Answer 18

Hadrons

Question 19

What is the exchange particle of the weak nuclear force?

Answer 19

The W boson (W+ or W-)

Question 20

What does the electromagnetic force act on?

Answer 20

Any particle with a charge

Question 21

When does the weak interaction occur?

Answer 21

When the quark character changes (when a quark turns into another quark), it affects all kinds of particles

Question 22

Which properties must be conserved in particle interactions?

Answer 22

1) Energy
2) Charge
3) Baryon number
4) Lepton number
5) Momentum
6) Strangeness (only for strong interactions)

Question 23

What is a hadron?

Answer 23

Both baryons and mesons are hadrons , they consist of 2 or more quarks held together by the strong nuclear force

Question 24

What are the classes of hadrons?

Answer 24

1) Baryons (3 quarks)

2) Mesons (1 quark 1 anti-quark)

Question 25

The pion can be the exchange particle of what force?

Answer 25

The strong nuclear force

Question 26

What particle does a kaon decay into?

Answer 26

A kaon decays into a pion

Question 27

What is significant about a proton?

Answer 27

1) Only stable baryon

2) All baryons decay into protons

Question 28

What are some examples of leptons ?

Answer 28

1) Electron
2) Muon
3) Neutrino
4) all antiparticles of the above

Question 29

What does a Muon decay into?

Answer 29

An electron

Question 30

What is the strangeness value of a strange quark?

Answer 30

-1

Question 31

Is strangeness conserved in the weak interaction?

Answer 31

No ,strangeness is only conserved in the strong nuclear interaction , in the weak interaction it can change by 0,-1 or +1

Question 32

Electron capture

Answer 32

A proton captures an inner shell electron and becomes a neutron and an electron neutrino with the W+ boson as the exchange particle

Question 33

Electron and proton collision

Answer 33

Electron and proton collide and a W- boson particle is exchanged. Electron turns into an electron neutrino and the proton becomes a neutron