Particles and radiation

Question 1

State what is meant by nucleon.

Answer 1

A particle that is in the nucleus.

Question 2

State what is meant by specific charge and its units.

Answer 2

The ratio of somethings charge to its mass (e.g. a nucleus or ion)
units = Ckg^-1

Question 3

What do you do to work out the specific charge of a nucleus?

Answer 3

(Proton no.) X 1.6 x 10^-19

/ (Mass no.) X 1.67 x 10^-27

Question 4

What do you do to work out the specific charge of an ion?

Answer 4

First workout its overall charge (e.g. lost 2 electrons = +2e or gained 1 electron = -1e etc etc.)
Overall charge (x 1.6 x 10^-19)
/ (Mass no.) X 1.67 x 10^-27

Question 5

What is the charge of a proton or an electron?

Answer 5

Proton = +1e = 1.60 x 10^-19
Electron = -1e = -1.60 x 10^-19

Question 6

What is the mass of a proton / neutron and an electron?

Answer 6

Proton / Neutron = 1.67 x 10^-27

Electron = 9.11 x 10^-31

Question 7

State what is meant by isotope.

Answer 7

An atom with the same number of protons but a different number of neutrons.

Question 8

State what is meant by ion.

Answer 8

An atom which has lost or gained electrons

It has an overall charge.

Question 9

When is the strong force repulsive and when is it attractive?

Answer 9

0>0.5fm = repulsive
0.5>3-5fm = attractive

Question 10

Why does the strong force have to be repulsive at short ranges?

Answer 10

So the protons don’t get pushed together.

Question 11

What does it mean if something has went through alpha decay?

Answer 11

It will have emitted an alpha particle
Meaning it has lost 2 protons and 2 neutrons
238 U –> 234 Th + 4 α
92 90 2

Question 12

If beta minus decay takes place in an atom what does this tell you about the nucleus?

Answer 12

It has a neutron rich nuclei.

Question 13

What happens during beta minus decay using an example?

Answer 13

A neutron turns into a proton emitting an electron (B- particle) and an anti-electron neutrino
n -> p + ß- + ̅νe

Question 14

If beta plus decay takes place in an atom what does this tell you about the nucleus?

Answer 14

It has proton rich nuclei.

Question 15

What happens during beta plus decay using an example?

Answer 15

A proton turns into a neutron releasing a positron (anti-electron) and an electron neutrino.
p -> n + β+ + νe

Question 16

Why was the neutrino predicted?

Answer 16

The beta particles were emitted with a range of different energies from the same isotope.
This did not allow the conservation of energy/mass.
Therefore another particle was predicted to make this decay possible.

Question 17

What does an antiparticle have?

Answer 17

the same mass as its particle.
Equal but opposite charge.
The same lifetime.

Question 18

What are photons?

Answer 18

Packets of energy that are mass-less and neutral.

Question 19

What is the equation for energy including planck’s constant and the speed of light in a vacuum?

Answer 19

E = hc/λ
Planck’s constant x v of light in vacuum
/ wavelength

Question 20

What does 1 electron volt = in joules?

Answer 20

1eV = 1.60 x 10^-19J

Question 21

What happens during annihilation?

Answer 21

A particle meets its anti-particle and they annihilate.

The mass of the particle and anti-particle is converted into energy in the form of 2 identical photons.

Question 22

Why are 2 photons give off during annihilation instead of 1?

Answer 22

2 photons are needed for momentum to be conserved.

Question 23

What happens during pair production?

Answer 23

A high energy photon vanishes creating a particle and its anti-particle (e.g. electron and positron) -> this conserves charge
Only occurs if the photon has enough energy to produce the total rest mass of the 2 particles.

Question 24

What is a fundamental particle?

Answer 24

A particle that cannot be broken down any further.

Question 25

What are leptons classed as?

Answer 25

Fundamental.

Question 26

What are hadrons and what are they classed as?

Answer 26

Particles which experience the strong force.

Non-fundamental.

Question 27

What is a baryon and give 2 examples with their quark compositions?

Answer 27

A hadron which will eventually contain a proton in their decay products.
They are made of 3 quarks.
proton = uud
neutron = udd

Question 28

What is a meson and give 2 examples with their quark compositions?

Answer 28

Hadrons that do not include protons in their decay sequence.
Made up of 1 quark and 1 antiquark.
pion (π0 or π+ or π−)
kaon (K0 or K+ or K-)
Kaons are strange so must have an strange or anti-strange quark

Question 29

What are the 3 types of leptons (with their neutrinos) and which is the heaviest and least heavy?

Answer 29

Electron, electron neutrino ( e , Ve ) (least heavy)
Muon, muon neutrino ( μ , Vμ )
Tau, tau neutrino ( t , Vt ) (heaviest)
All leptons have a charge of -1 and all neutrinos have a charge of 0.

Question 30

For a particle interaction to be possible, What must be conserved?

Answer 30

1. Mass/energy
2. Momentum
3. Charge
4. Baryon number
5. Lepton number
   + strangeness in strong & EM interactions, in weak = can change by -1 or 0 or +1

Question 31

What are the 3 types of quarks you need to know about?

Answer 31

Up (& anti-up)
Down (& anti-down)
Strange (& anti-strange)