Nuclear Physics

Question 1

What are the three types of radiation?

Answer 1

Alpha
Beta
Gamma

Question 2

What must be measured first before a source’s count rate is tested?

Answer 2

Background radiation

Question 3

How do the radiation types deflect in a magnetic field?

Answer 3

Alpha and beta deflect in opposite directions
Beta deflects more than alpha due to its smaller mass
Gamma is not deflected

Question 4

Define intensity of radiation

Answer 4

The radiation energy per second passing normally through unit area

Question 5

Describe the alpha particle scattering experiment

Answer 5

Alpha particles were fired at very thin gold in a vacuum. A phosphorous screen around the outside showed where the alpha particles traveled

Question 6

Describe the observations and conclusions from the alpha particle scattering experiment

Answer 6

Most of the fast, highly charged alpha particles went straight through undeflected - SUGGESTS THAT MOST OF THE ATOM IS EMPTY SPACE
Some of the alpha particles were deflected through large angles. - SUGGESTS THAT THERE IS A CONCENTRATED POSITIVE MASS SOMEWHERE IN THE ATOM.
A very small number of alpha particles were deflected backwards - SUGGESTS THAT THE CONCENTRATED MASS IS MINISCULE COMPARED TO THE SIZE OF THE REST OF THE ATOM, BUT CONTAINS MOST OF THE MASS

Question 7

In a nuclear reaction what must be conserved?

Answer 7

Mass/Energy
Momentum
Charge

Question 8

Describe an alpha particle

Answer 8

2 protons and 2 neutrons or a helium nucleus
relative mass = 4
relative charge + 2
Highly ionising
Stopped by skin, paper 10 cm air

Question 9

Describe a beta particle

Answer 9

an electro emitted from the nucleus
relative mass = almost 0
relative charge -1
Moderatly ionising
Stopped by mm’s of aluminium or 1 meter of air

Question 10

Describe a gamma wave

Answer 10

electromagnetic wave moving at the speed of light
relative mass = 0
relative charge 0
Very weakly ionising
Reduced by cm’s lead or meters of concrete

Question 11

What changes does alpha decay cause to the daughter nucleus?

Answer 11

Mass number decreases by 4
Proton number decreases by 2

Question 12

What changes does beta decay cause to the daughter nucleus?

Answer 12

Mass number stays the same
Proton number increases by 1

Question 13

What changes does gamma decay cause to the daughter nucleus?

Answer 13

Mass number stays the same
Proton number stays the same. the nucleus just losses some energy

Question 14

What changes happen in beta decay?

Answer 14

A neutron decays into a proton creating a beta particle and an electron antineutrino.
A down quark decays into an up quark.

Question 15

Define activity

Answer 15

The rate at which any substance emits radioactive particles is called the activity. The activity is measured in Becquerels (Bq)

Question 16

Define count rate

Answer 16

The count rate is simply the number of particles that are counted by a Geiger counter (or some kind of measuring device)

Question 17

What factors will affect the activity of a substance?

Answer 17

The number of particles there are in the substance
The natural tendency of a substance to decay (i.e. some substances are naturally more likely to decay more than others)

Question 18

Define half life

Answer 18

The half life of a substance is the time it takes for half the number of particles in the substance to decay. It can also be seen as the time it takes for the activity of a substance to fall to half its current value.

Question 19

Define the atomic mass unit

Answer 19

It is equal to exactly 1/12th the mass of a carbon 12 atom

Question 20

Define the electronvolt

Answer 20

The electronvolt (eV) is the energy gained when 1 electron accelerates through a p.d. of 1 volt

Question 21

How can you convert from eV to J?

Answer 21

1 eV = 1.6 x 10-19 J

Question 22

how can you convert from MeV to eV

Answer 22

1 x 106 eV = 1MeV

Question 23

Define mass defect

Answer 23

The difference between the mass of an atom and the mass of its individual particles is known as the Mass defect, Δm.

Question 24

Define binding energy

Answer 24

The binding energy of a nucleus is the energy that would be required to separate a nucleus into its separate constituents

Question 25

Define binding energy per nucleon

Answer 25

average energy needed to “break off” just one nucleon from the nucleus.

Question 26

What is the role of fuel rods in a nuclear reactor?

Answer 26

Contained in the reactor core and generally made of enriched uranium. Act as fuel source of the fission reactor

Question 27

What is the role of the moderator in a nuclear reactor?

Answer 27

Usually made of carbon and also part of the reactor core. Slows down neutrons within the reactor core allowing them to fuse with the uranium and make fission reactions

Question 28

What is the role of the control rods in a nuclear reactor?

Answer 28

Made of boron, which can absorb neutrons. These can be lowered into the reactor to control the rate of fission.

Question 29

What is the role of the coolant in a nuclear reactor?

Answer 29

The coolant absorbs the heat from the fission reactions. It is then used to heat up water and turn it into high pressure steam

Question 30

What is the role of the turbine and generator in a nuclear reactor?

Answer 30

The turbine is turned by the high pressure steam which, in turn, turns the generator. This generates electricity.