Particles and Radiation

Question 1

Specific Charge

Answer 1

Charge ÷ mass (Ckg⁻¹)

Question 2

Isotopes

Answer 2

Doesn’t affect chemical properties
Affects stability of nucleus
More neutrons compared to protons, more unstable nucleus
Unstable nuclei may be radioactive and decay to make more stable`

Question 3

Hydrogen isotopes examples

Answer 3

Protium - 1p, 0n
Deutrium - 1p, 1n
Titrium - 1p, 2n

Question 4

Nuclear decay

Answer 4

Unstable nuclei will emit particles to become more stable

Question 5

Alpha decay

Answer 5

Only very big atoms (>82 protons) as strong nuclear force can’t keep stable.
Emit alpha particle
Have very short range (only a few cm in air).
Use a Geiger or Spark counter to observe.

Question 6

Beta-minus decay

Answer 6

Only in 'neutron rich' isotopes 
Emit electron and antineutrino
Neutron changes to proton
Range of several metres in air
Caused by weak interaction
Antineutrino carries away missing energy

Question 7

Hypothesis of neutrinos

Answer 7

Energy of particles not conserved in beta decay
Wolfgang Pauli (1930) suggested another particle with no charge and little to no mass carried away the missing energy

Question 8

Forces in the nucleus

Answer 8

Electromagnetic
Gravitational
Strong nuclear

Question 9

Electromagnetic Force

Answer 9

Causes protons to repel

Question 10

Gravitational force

Answer 10

Causes all the nucleons to attract due to their masses

Not strong enough to overcome repulsion of EM

Question 11

Strong Nuclear force

Answer 11

Other attractive force larger than EM force counteracts repulsion
Very short range (up to a few fm)
Repulsive up to 0.5 fm
Strongest from 0.5 - 3 fm
1 fm = maximum attraction

Question 12

EM radiation Spectrum

Answer 12

Rich Men In Venice Use eXtra Gold

decreasing wavelength

Question 13

Photons

Answer 13

Max Plank suggested EM waves only be RELEASED in discrete packets (called quanta)
Einstein suggested can only EXIST in discrete packets (called photons)
E = hf = hc/λ
E is energy (J), h is Plank’s constant (6.63x10⁻³⁴ Js), f is frequence (Hz)

Question 14

Pair production

Answer 14

Energy into mass
Equal amounts of matter and antimatter
Requires enough energy to produce particle and antiparticle
Eₘᵢₙ = 2E₀

Question 15

Annnihilation

Answer 15

Particle meets its antiparticle
All mass of particle and antiparticle is converted to energy as 2 gamma ray photons
Min energy of particles produced by is rest energy of the pairs split between 2 gamma rays Eₘᵢₙ = E₀

Question 16

Hadrons

Answer 16

Particles that can feel the strong force
Not fundamental particles as they are made up of 3 quarks
There are two types of hadrons - baryons and mesons

Question 17

Baryons

Answer 17

Protons and neutrons are baryons

All baryons eventually decay to become protons

Question 18

Baryon number

Answer 18

The baryon number is a quantum number that must be conserved

Question 19

Neutron decay

Answer 19

When a neutron decays, it forms a proton, and electron and an antineutrino

Question 20

Mesons

Answer 20

Pions and kaons

Can be detected in cosmic ray showers

Question 21

Pions

Answer 21

The lightest mesons
Three variations each with different electric charges
These are the exchange particles of the strong force

Question 22

Kaons

Answer 22

Heavier and more unstable than pions

Have a very short lifetime and decay into pions

Question 23

Leptons

Answer 23

Fundamental particles that dont feel the strong force
only interact with other particles via the weak interaction
Muons eventually decay into electrons

Question 24

Lepton numbers

Answer 24

Quantum numbers and must also bre conserved

Electron and muon types of lepton have to be counted separately

Question 25

Strange particles

Answer 25

Created via the strong interaction in which strangeness is conserved
Conservation of strangeness means that strange particles can only be created in pairs
A quantum number so must be conserved except in the weak interaction

Question 26

Conservation of particles

Answer 26

Energy, momentum are always conserved as well as the four quantum numbers

Question 27

Conservation of quantum numbers

Answer 27

Total before must equal total after.

Except strangeness which is only conserved for strong interactions and SOME weak but not always

Question 28

Quarks

Answer 28

Up, down and strange

The properties of particles depends on the properties of the quarks it’s made up of

Question 29

Quark composition of baryons

Answer 29

Made up of three quarks

Charge and baryon number of a baryon is the total charge and baryon number of the particle

Question 30

Quark composition of mesons

Answer 30

Made up of one quark and one antiquark.
Pions are variation sof up, down, antiup and antidown quarks
Kaons have strangeness so have a strange quark and one other quark

Question 31

Quark confinement

Answer 31

It isn’t possible to get a quark by itself

Question 32

Weak interaction

Answer 32

Beta minus decay

Beta plus decay

Question 33

Beta minus decay (quarks)

Answer 33

A neutron changes into a proton which means that a d quark changes to a u quark
Only weak interaction can do this

Question 34

Beta plus decay (quarks)

Answer 34

A proton changes to a neutron which means that a u quark changes to a d quark

Question 35

Particle exchange

Answer 35

virtual particles that only exist for a short time

all forces caused by four fundamental forces each with their own exchange particle

Question 36

Type of interaction, Gauge boson and particles affected

Answer 36

Strong - Pions - Hadrons only
EM - Virtual photons - Charged particles
Weak - W⁺, W⁻ bosons - All types

Question 37

Particle interaction diagrams

Answer 37

Exchange particles are wiggly lines
Other particles are straight lines
Incoming start at the botton and move upwards
Baryons stay on one side, leptons on the other
W bosons carry charge from on eside to the other