Particles and Radiation

Question 1

What is specific charge, its formula and units

Answer 1

Specific charge of a particle is a charge-mass ratio

specific charge = charge/mass (Ckg^-1)

Question 2

Define isotopes

Answer 2

Atoms with the same number of protons but different number of neutrons

Question 3

What is strong nuclear force

Answer 3

A force that keeps nuclei stable by counteracting the electrostatic force of repulsion between protons
(attractive from 0.5 to 3fm, repulsive below 0.5fm)
- has a very short range

Question 4

Sim/diff of corresponding particles/antiparticles

Answer 4

Same mass, same rest energy
all other properties are opposite (e.g charge)

Question 5

What are photons

Answer 5

Electromagnetic radiation which transfer energy and have no mass
E = hf (energy of photon is proportional to its frequency)

Question 6

Explain the process of annihilation

Answer 6

Particle and corresponding particle collide where mass is converted to energy
2 photons are released in opposite directions to conserve momentum
Excess energy is used as kinetic energy

Question 7

Explain the process of pair production?

Answer 7

When a photon is converted to an equal amount of matter and antimatter
Only occurs when photon has greater energy then total rest energy as excess energy is converted into Ek

Question 8

What are the four fundamental forces

Answer 8

Gravity, electromagnetic, weak nuclear and strong nuclear

Question 9

What are exchange particles?

Answer 9

Forces between particles are caused by exchange particles
Exchange particles carry energy and momentum

Question 10

What is weak nuclear force

Answer 10

Responsible for beta decay, electron capture and electron-proton collisions
Exchange particle is W+/- bosons

Question 11

Which particles are fundamental particles and what does this means?

Answer 11

Leptons are fundamental particles and this means they cannot be broken down further

Question 12

Which type of particle experiences strong nuclear force

Answer 12

Only hadrons

Question 13

Which particle type does not experience strong force and give examples

Answer 13

Leptons e.g electrons, neutrinos and anti-neutrinos

Question 14

Which particles is the only stable baryon

Answer 14

Proton as all other baryons will eventually decay into a proton.

Question 15

What particle can decay into electrons

Answer 15

Muons (aka heavy electrons)

Question 16

What do you know about strange particles?

Answer 16

They’re produce via strong nuclear interactions but decay via weak interactions
(e.g kaons decays into pions through weak interaction)

Strong interactions = strangeness is always conserved
Weak interactions = can change by 0 +1 -1
Strange particles must be created in pairs

Question 17

What is the baryon number of quarks in only baryons

Answer 17

1/3 (including u, d and strange quarks)

Question 18

What is the charge and strangeness of a strange quark

Answer 18

-1/3e (Q)
-1 strangeness

Question 19

What are the quark combination of all kaons

Answer 19

K0 = down + antistrange (strangeness = +1)
K+ = Up + antistrange (strangeness = +1)
K- = anti up + strange (strangeness = -1)

Question 20

Quark combination of all pions (remember to conserve charge)

Answer 20

pi0 = u+/u or d+/d
pi+ = up+/down
pi- = /u + d
Strangeness is all 0

Question 21

List properties that always should be conserved

Answer 21

Energy and momentum
Charge
baryon number
leptons number
(strangeness only in strong interaction)

Question 22

Strangeness can only be changed by how much in a weak interaction

Answer 22

By one (-1, +1)

Question 23

Why is an antineutrino conserved in a beta minus decay

Answer 23

This is to conserve the lepton number

Question 24

When you have a higher frequency what happens to the size of the wavelength

Answer 24

It decreases

Question 25

Can protons experience a weak nuclear force

Answer 25

Yes because electrons are able to interact with them

Question 26

Can a pion 0 experience a electromagnetic force

Answer 26

No because it doesn’t have a charge!

Question 27

Can a neutrino experience a strong nuclear force?

Answer 27

No because it is a lepton, only hadrons experience SNF.

Question 28

In electron capture what is the exchange particle and why?

Answer 28

The exchange particle is a W+ boson because the protons positive charge is taken away which results in a neutrino.

Question 29

What doesn’t change in a beta minus decay

Answer 29

The mass number

Question 30

What interaction produces strangeness and what interaction decays strangeness into non-strange particles

Answer 30

Strong - production of strangeness (as strangeness is conserved)
Weak - strangeness is lost (via decay)

Question 31

What do mesons eventually decay into

Answer 31

Kaons eventually decays into pions

Question 32

What are some key difference between internal conversion and beta decay

Answer 32

• in beta decay an anti neutrino is produced unlike conversion
• in beta decay the proton and neutron number change unlike conversion
• internal conversion is electrostatic force whilst beta decay is weak interaction

Question 33

Explain why there is a minimum rest energy in pair production

Answer 33

At least the rest mass of the two corresponding particles is needed

Question 34

Define specific charge

Answer 34

The ratio of charge to mass of the nucleus

Question 35

What is order of magnitude for the diameter of an atom

Answer 35

10^-11m