Nuclear Physics

Question 1

What is the meaning for why most alpha particles passed straight through the gold foil?

Answer 1

Most of the atom is empty space.

Question 2

What is the meaning for why some alpha particles were deflected between 0-90 degrees by the gold foil?

Answer 2

Highly positively charged core.

Question 3

What is the meaning for why very few alpha particles were reflected >90 degrees by the gold foil?

Answer 3

Nucleus is very small, dense and contains most of the mass of the atom.

Question 4

What is the range of an alpha particle in air?

Answer 4

5-10 cm

Question 5

What is the range of a beta particle in air?

Answer 5

1m

Question 6

What law does a gamma particle follow in air?

Answer 6

Inverse square law.

Question 7

What can an alpha particle be stopped by?

Answer 7

Piece of paper.

Question 8

What can a beta particle be stopped by?

Answer 8

A few mm of aluminium.

Question 8

Which radioactive particle is deflected most in a magnetic field?

Answer 8

Alpha

Question 9

What can a gamma particle be stopped by?

Answer 9

A few cm of lead.

Question 10

What is the equation for electron capture?

Answer 10

X + e to Y + Ve

Question 11

What is intensity?

Answer 11

Energy per second on an area.

Question 11

What are some applications for radioactive substances?

Answer 11

• Detecting underground leaks.
• Modelling oil reservoirs.
• Uptake of fertilisers by plants.
• Monitoring uptake of iodine in thyroid gland.

Question 12

What is carbon dating?

Answer 12

Using trees / plants to measure activity of dead samples, can calculate age of tree.

Question 12

What is argon dating?

Answer 12

Using rocks containing trapped argon gas, measure proportion of argon to potassium to calculate age of rock.

Question 13

What is radioactive decay?

Answer 13

Random disintegration of an unstable nucleus by emission of particles or EM radiation.

Question 14

What is the activity of a substance?

Answer 14

The number of unstable radioactive nuclei decaying per second.

Question 15

What is the decay constant?

Answer 15

Probability of a nucleus decaying in a time period.

Question 16

What is the half-life of a substance?

Answer 16

Time taken for half of the number of radioactive nuclei to decay.

Question 17

What is 1 Bq?

Answer 17

1 decay per second.

Question 18

What is the gradient of a graph of ln N against t (nuclear physics)?

Answer 18

Negative of the decay constant.

Question 19

What is an N-Z graph?

Answer 19

Graph of neutron against proton number, visually shows the stability of isotopes.

Question 20

What does metastable mean?

Answer 20

Not in lowest energy state but not quickly transitioning to lower level (can be measured and tested on).

Question 21

What is the half-life of Technetium-99m and its nature of decay?

Answer 21

6 hours, decays by gamma to ground state.

Question 22

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

Answer 22

Slows down neutrons produced by fission by forcing elastic collisions.

Question 23

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

Answer 23

Reduce the reaction rate by absorbing neutrons.

Question 24

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

Answer 24

Removes heat from core and transfers is to generators / environment.

Question 25

What properties does a moderator need?

Answer 25

Low neutron absorption cross-section.

Question 26

What properties do control rods need?

Answer 26

High ability to absorb neutrons, high melting point.

Question 27

What properties does a coolant need?

Answer 27

Can carry large amounts of heat, poor neutron absorber.

Question 28

What is an example of a moderator?

Answer 28

Water, graphite.

Question 29

What material is an example of a control rod?

Answer 29

Boron, Cadmium.

Question 29

What is an example of a coolant?

Answer 29

Water, Helium.

Question 30

What is meant by induced fission?

Answer 30

A stable nucleus splits into smaller nuclei after absorbing slow-moving neutron.

Question 31

What is a chain reaction?

Answer 31

Produced neutrons go on to cause more fission.

Question 32

What is critical mass?

Answer 32

Minimum mass of fuel required to maintain a steady chain reaction.

Question 33

What happens when the mass of the fuel is less than the critical mass?

Answer 33

Reaction stops (subcritical mass).

Question 34

What happens when the mass of the fuel is greater than the critical mass?

Answer 34

Explosion (supercritical mass).

Question 35

How do you convert from mass to number of nuclei?

Answer 35

Divide given mass by molar mass to find mole number. Then multiply moles by avogadro's constant.

Question 36

How do you calculate radius by closest approach?

Answer 36

Set the kinetic energy equal to the potential energy.

Question 37

What is the mass defect?

Answer 37

Difference in mass of nucleons and mass of nucleus.

Question 37

Which is heavier: mass of nucleons or mass of nucleus?

Answer 37

Mass of nucleons.

Question 38

What is the binding energy of an atom?

Answer 38

Energy required to separate a nucleus into its constituents.

Question 39

What is the most stable nucleon number?

Answer 39

56 (Fe)

Question 40

What is vitrification?

Answer 40

When nuclear waste is mixed with molten glass and made solid to be stored safely.