Nuclear Physics

Question 1

What is an ion?

Answer 1

An electrically charged atom formed by the loss or gain of electrons.

Question 2

What is a proton number?

Answer 2

Also known as the atomic number, it is the number of protons in an atom.

Question 3

What does the proton number determine?

Answer 3

What element an atom is

Question 4

What is an isotope?

Answer 4

Atoms of the same element that have the same number of protons but a different number of neutrons.

Question 5

What is the relationship between proton number and relative charge?

Answer 5

The proton number is equal to the relative charge on the nucleus.

Question 6

Define nuclear fission

Answer 6

The splitting of a large nucleus into smaller nuclei with the release of energy.

Question 7

What can be released in nuclear fission?

Answer 7

Neutrons and gamma radiation

Question 8

Define nuclear fusion?

Answer 8

When two light nuclei join together to form a heavier nucleus with the release of energy.

Question 9

How are positive and negative ions created?

Answer 9

Positive ions are created when an atom looses electrons.
Negative ions are created when an atom gains electrons.

Question 10

Where is the energy from nuclear fusion from?

Answer 10

The energy produced during nuclear fusion comes from a very small amount of the particles mass being converted to energy.

Question 11

What is background radiation?

Answer 11

The radiation that exists around us all the time

Question 12

What sources make a significant contribution to background radiation?

Answer 12

• radon gas (in the air)
• rocks and buildings
• food and drink
• cosmic rays

Question 13

Can ionising nuclear radiation be measured?

Answer 13

Yes, using a detector connected to a counter.

Question 14

What is counts/s and counts/minute?

Answer 14

The unit used to measure activity.

Question 15

What are two properties of radiation from a nucleus?

Answer 15

Spontaneous - can occur at anytime and is not affected by anything
Random in direction

Question 16

Properties of alpha emission?

Answer 16

• they have 2 protons and 2 electrons and are identical to a helium nucleus.
• they have a very strong ionising effect
• they are weakly penetrating and can be stopped by a thick sheet of paper or centimetres of air
• in an electrical field, they are deflected towards a negatively charged plate.
• in a magnetic field, their deflection is determined based on the left-hand rule

Question 17

Properties of beta emissions

Answer 17

• They a electrons
• they have a mildly strong ionising effect
• they are strong in penetrating but can be stopped by a few millimetres of aluminium.
• they are deflected towards the positive plates in an electric field.
• they are deflected strongly in magnetic fields in a direction determined by left hand rule.

Question 18

Gamma rays are:

Answer 18

• electromagnetic waves
• have no charge
• very weak ionising effect
• no mass
• very penetrating and weakened by thick piece of lead or concrete.
• not deflected by magnetic or electric fields.

Question 19

How is ionising effect related to kinetic energy and electric charge?

Answer 19

For kinetic energy, alpha particles have a higher mass and therefore have a higher ke fo exert more force on electrons
For charge, they have a greater electrical charge then they have a greater ionising effect

Question 20

What is radioactive decay?

Answer 20

A change in an unstable nucleus (isotope) that can result in the emission of a-particles, b-particles or y-radiation.
These are spontaneous and random
OR
A process where the nucleus of an unstable isotope emits radiation in order to become more stable, causing a change in the nucleus.

Question 21

What happens to the nucleus during a-decay or b-decay?

Answer 21

The nucleus changes to that of a different element.

Question 22

What makes isotopes radioactive?

Answer 22

Due to excess neutrons in the nucleus and/or the nucleus being too heavy.

Question 23

What is the effect of alpha and beta decay on a nucleus?

Answer 23

ALPHA
- increases the stability of the nucleus
- but reduces the proton number by 2 and mass number by 4

BETA
- increase in stability as well
- neutron —> proton + electron
- an increase in proton number changing the element but not the mass.

Question 24

How do you determine a correct count rate?

Answer 24

Detector reading - background reading

Question 25

What are some effects of ionising nuclear radiations on living things?

Answer 25

Cell death
Mutations
Cancer

Question 26

What are some safety precautions to take when dealing with radioactive sources?

Answer 26

• Reduce exposure time
• increase distance between source and living tissue
• use shielding to absorb radiation.

Question 27

Describe how radioactive materials are moves, used and stored in a safe way.

Answer 27

Using lead or lead lined containers that are locked.

Question 28

What is half life?

Answer 28

The half life of a radioactive isotope is the time taken for half the nuclei in any given sample to decay.

Question 29

What is activity and its SI unit?

Answer 29

The average number of disintegrations per second.
Becquerel (Bq)
Also counts per minute or second

Question 30

What do you do differently to calculate half-life from decay curves from which background radiation has not been subtracted?

Answer 30

Remove the background count from all values before calculating the half life.

Question 31

Household fire (smoke) alarms

Answer 31

Use alpha particles with a long half-life.
A circuit set up with two plates and ionizing alpha particles in between.
When smoke comes in contact with the particles, the ions attach to them and current stops flowing hence, triggering an alarm.

Question 32

Irridiating food to kill bacteria and sterilisation of equipment.

Answer 32

Using gamma rays and Cobalt-60 with a half life of 5 years.
Used to kill bacteria (living things) found in the equipment or food.

Question 33

Diagnosis and treatment of cancer using gamma rays.

Answer 33

• used to penetrate the body and kill cancer cells. Gamma rays in a high energy beam concentrated at the cancer tumour.
• to diagnose, use gamma rays with a short half life because they are injected into the body.

Question 34

Measuring and controlling thicknesses of materials.

Answer 34

• beta particles with a long half life
• beta particles pass through sheets of material
• if the reading decreases more than normal, sheet is too think
• if the reading increases more than normal, the sheet is too thin.

Question 35

How do you determine the charge of a beta particle when an alpha is given?

Answer 35

Divide by two and make it negative.
Because an electron is half the charge of an alpha.