nuclear physics

Question 1

how much bigger is the atom than nucleus?

Answer 1

approx 100,000 times

Question 2

what letter is associated with proton number?

Answer 2

Z

Question 3

What is a nucleon?

Answer 3

A particle that makes up the nucleus (protons and neutrons only)

Question 4

what letter represents nucleon number?

Answer 4

A

Question 5

What is the strong nuclear force?

Answer 5

The force that holds the nucleus together
(it must overcome the electrostatic force of repulsion between protons, but not so much as to cause the nucleus to collapse)

Question 6

describe the range of the strong force

Answer 6

repulsive: up to 0.5fm
attractive: up to 3fm

Question 7

what is the same and different about particles and antiparticles?

Answer 7

• same mass
• different charge

Question 8

what is the name of an electron antiparticle?

Answer 8

positron

Question 9

what is a hadron?

Answer 9

fundamental particle affected by strong nuclear force

Question 10

what are hadrons made of

Answer 10

quarks

Question 11

what are the classes of hadrons?

Answer 11

baryons (3 quarks)
mesons (2 quarks)

Question 12

what are two examples of baryons?

Answer 12

proton and neutron

Question 13

what are the four fundamental forces?

Answer 13

• strong nuclear
• weak nuclear
• electrostatic
• gravity

Question 14

which forces are hadrons subject to?

Answer 14

it can be all four fundamental forces
(only charged hadrons, protons, will be subject to electrostatic forces)

Question 15

what are leptons?

Answer 15

fundamental particles which are not subject to the strong nuclear force
(only weak)

Question 16

Give 3 examples of leptons

Answer 16

• electrons
• muons
• neutrinos
  (and their corresponding antiparticles)

Question 17

state the quark composition of protons and neutrons

Answer 17

• UUD for proton
• UDD for neutron

Question 18

Can quarks ever be found on their own?

Answer 18

no

Question 19

What is meant by beta minus decay?

Answer 19

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

Question 20

which quark decays in a beta minus decay?
what does it turn into?

Answer 20

a DOWN quark turns into an UP quark

Question 21

what quantities MUST be conserved during decay of particles?

Answer 21

• charge
• mass
• lepton number
• baryon number

Question 22

what are the features of radioactive decay?

Answer 22

• spontaneous and random
• can’t be predicted when nucleus will decay

Question 23

what features may cause a nucleus to decay?

Answer 23

• too many/few neutrons
• too heavy (too many nucleons)
• too much energy

Question 23

what quantities MUST be conserved during decay of particles?

Answer 23

• charge
• mass
• lepton number
• baryon number

Question 25

name 4 types of radiation

Answer 25

- alpha - beta plus - beta minus - gamma

Question 26

what is an alpha particle?

Answer 26

- two protons and two neutrons (same as helium nucleus)

Question 27

how far does beta typically penetrate in air?

Answer 27

50cm-1m

Question 28

what materials would be needed to investigate whether a radioactive source was releasing alpha, beta or gamma?

Answer 28

- alpha - paper - beta - 5mm thick aluminium - gamma - thick lead sheet

Question 29

if a particle undergoes alpha decay, what are the remaining atomic numbers?

Answer 29

nucleon number = A - 4 atomic number = Z - 2

Question 30

In beta plus decay, how does the atomic number change?

Answer 30

It decreases A proton turns into a neutron and positron so mass is constant but atomic number decreases

Question 31

What is activity of a source

Answer 31

The number of radioactive decays per second (measured in Bq)

Question 32

define half life

Answer 32

average time taken for the activity of a sample to half

Question 33

what isotope is commonly used to find out how old things are

Answer 33

carbon-14 for carbon dating

Question 34

What happens when a particle and antiparticle meet?

Answer 34

Annihilation - when they meet they will annihilate eachother and release 2 gamma rays - two rays are released in order to conserve momentum - the mass of the particles will transform into the energy equivalent

Question 35

what is pair production?

Answer 35

When a gamma ray has enough energy to produce a particle and its antiparticle.

Question 36

Why does beta plus decay have a very low penetration?

Answer 36

Because it will annihilate with matter almost immediately

Question 37

what is the mass defect?

Answer 37

The difference between the total mass of all the nucleons seperately compared to the mass of the nucleus.

Question 38

Why is there a mass defect?

Answer 38

Because energy is released as the nucleons bind together into a nucleus.

Question 39

What is binding energy?

Answer 39

The energy required to seperately a nucleus into its constituent parts

Question 40

What does a low binding energy per nucleon mean?

Answer 40

Less stable so not much energy would be required to separate the nucleus (more likely to decay)

Question 41

What is nuclear fission

Answer 41

Where an unstable nucleus splits into 2 smaller nuclei (binding energy increases therefore overall process releases energy)

Question 42

What is fusion

Answer 42

When two nuclei fuse together to create larger nuclei (larger binding energy per nucleon compared to the old nuclei therefore energy is released in the process)

Question 43

which process releases the most energy out of fusion and fission?

Answer 43

fusion as the change in binding energy is very drastic

Question 44

why is it difficult to make fusion occur on earth?

Answer 44

- large repulsion between the two positively charged nuclei therefore a lot of energy required to overcome repulsion - hard to get material to withstand heat and be cost effective

Question 45

How is fission used in nuclear reactors?

Answer 45

Rods of uranium-235 absorb neutrons and become unstable and then split into two daughter nuclei. It also releases 2 or 3 more neutrons. These then go on to be absorbed by another uranium atom

Question 46

what is the purpose of the moderator?

Answer 46

- slow down neutrons so they travel slow enough to be absorbed by uranium - this happens through elastic collisions between moderator and the nucleus

Question 47

Why are control rods essential for a nuclear power station?

Answer 47

They stop the chain reaction being out of control - they absorb neutrons so that only 1 of the neutrons released in each reaction can go on to be absorbed by another uranium - if not the nuclear reactor would overheat as too many reactions would occur at once

Question 48

what material can be used as a moderator?

Answer 48

water - small mass so can’t absorb neutrons easily

Question 49

What is a chain reaction?

Answer 49

When one neutron from each decay goes on to decay again - amount of energy released is constant

Question 50

how is nuclear waste disposed of?

Answer 50

- put in cooling ponds - then sealed in steel containers and potentially stored underground or underwater

Question 51

One environmental benefit and risk of nuclear power

Answer 51

- no release of greenhouse gases, no contribution to global warming - nuclear explosions