Topic 6 - Radioactivity

Question 1

Background Radiation

Answer 1

• Constant emission of ionising radiation from space and environment

Question 2

Origins of background radiation in Earth and Space

Answer 2

• Earth : Radon, Foods, X-rays, Gamma-rays, Cancer treatment
• Space : Cosmic Rays

Question 3

How to detect radioactivity through Geiger-Muller Tube

Answer 3

• Radiation enter through tube and ionises gases inside, which forms a current to flow, which makes a clicking noise

Question 4

How to detect radioactivity through Photographic Film

Answer 4

• The ionising radiation causes changes in the crystals in the film that can be seen

Question 5

How is ionising radiation released?

Answer 5

• Unstable nuclei in a random process

Question 6

Beta +/- is an electron emitted from the…

Answer 6

nucleus

Question 7

The most ionising decay is…

Answer 7

alpha

Question 8

The most penetrative decay is…

Answer 8

gamma

Question 9

1st atomic model

Answer 9

Indivisible mass

Question 10

2nd atomic model

Answer 10

JJ Thompson - Plum Pudding

Question 11

3rd atomic model

Answer 11

Nuclear model

Question 12

Modern atomic model

Answer 12

Bohr model

Question 13

Beta +/- decay release what electric charges

Answer 13

minus = neutrons -> protons + electrons
plus = protons -> neutrons + positron

Question 14

All nuclear transmission charge and mass numbers

Answer 14

Alpha P=-2 M=-4
Beta - P=1 M=0
Beta + P=-1 M=0
Gamma P=0 M=0
Neutron P=0 M=-1

Question 15

Uses of radiation:

Answer 15

• Smoke alarm
• Irradiating food
• Sterilisation of equipment
• Tracing and gauging thicknesses
• Diagnosis and treatment of cancer

Question 16

How do smoke alarms work?

Answer 16

• Smoke enters alarm
• Breaks circuit formed from radiation
• Bell rings

Question 17

Precautions taken to ensure safety of people exposed to radiation

Answer 17

• Keep distance
• Reduce time
• PPE (e.g. radiation suit)
• Store underground

Question 18

Contamination

Answer 18

• Unwanted radioactive materials in or on a body

Question 19

Irradiation

Answer 19

• Body exposed to but not physically touching

Question 20

Properties of External Radiation

Answer 20

• Radioactive isotope from machine out of body
• Very precise
• Takes many sessions
• Causes skin irritation, fatigue and damage to nearby tissue

Question 21

Properties of Internal Radiation

Answer 21

• Placed inside or near tumour
• Better for irregular shaped tumours or tumours in a vital location
• Short treatment (few sessions)
• Causes infections and damage to internal organs

Question 22

Uses of radioactive substances in the diagnosis of medical conditions:

Answer 22

• Tracers : Emits radiation, which can be tracked to check if organs are working correctly
• PET Scanners: Provide detailed three-dimensional images of metabolic activity in tissues

Question 23

Isotopes used in PET scanners have to be produced nearby because:

Answer 23

• Short half-life, so they decay quickly

Question 24

What are the advantages of using nuclear power for electricity generation

Answer 24

Nuclear power stations:
- Produce no polluting gases
- Far less fuel required
- Highly reliable

Question 25

What are the disadvantages of using nuclear power for electricity generation

Answer 25

Nuclear power stations: - Produce radioactive waste which is dangerous and expensive to deal with - Can have catastrophic consequences on the environment and people in the event of a nuclear meltdown - Expensive start-up and shut down cost

Question 26

Nuclear reactions can be used as:

Answer 26

- a source of energy

Question 27

The products of nuclear fission are all:

Answer 27

- radioactive

Question 28

How fission works:

Answer 28

- Neutron collides with large nucleus - Nucleus splits - 2 smaller daughter nuclei are released with 2 or more neutrons - Gamma rays are emitted (energy released)

Question 29

Principle of a controlled nuclear chain reaction:

Answer 29

- Using nuclear reactions to produce ongoing energy.

Question 30

How is a nuclear chain reaction controlled?

Answer 30

- Neutron Moderator (slows down neutrons) - Control Rods (absorbs excess neutrons)

Question 31

Electricity is made from thermal energy from the chain reaction. How?

Answer 31

- Nuclear reactor generates thermal - Boiler makes steam with thermal - Turbine uses steam to turn thermal to kinetic - Generator turns kinetic into electricity

Question 32

What is a star's energy source?

Answer 32

- Nuclear fusion

Question 33

How fusion works:

Answer 33

- 2 smaller nuclei fuse to create a larger nuclei - Results in a loss of mass - Process releases energy

Question 34

Nuclear fusion does not happen at low temperatures and pressures because:

Answer 34

- Protons repel and their kinetic energy won't be high enough

Question 35

The conditions of fusion is difficult to maintain for practical and economic use because:

Answer 35

- Such high temperatures and pressure required for fusion are hard to contain, meaning only a small amount of fusion occurs