Radioactivity Part 2

Question 1

Describe background radiation

Answer 1

Low-level radiation all around us.
Examples:
Cosmic rays
Past nuclear weapons tests
Radon gas
Medical sources
Bananas

Question 2

What are the 5 different ways of detecting radioactivity?

Answer 2

1. Photographic plates
2. Geiger-Muller tubes
3. A spark counter
4. Electroscope
5. Cloud chamber

Question 3

Define radioactive decay

Answer 3

When the nucleus of an atom emits radiation. Completely random process.

Question 4

What are the 3 types of radiation?

Answer 4

Alpha radiation
Beta radiation
Gamma radiation

Question 5

Describe alpha radiation

Answer 5

Alpha particle
Helium nucleus
Two protons and two neutrons
Positively charged

Question 6

Describe beta radiation

Answer 6

Beta particle
High speed electron
Negatively charged
Emitted from the nucleus (not the shells)

Question 7

Describe gamma radiation

Answer 7

High frequency electromagnetic wave
Has no charge
Similar to x-rays but with smaller wavelength
Travel at the speed of light
No mass

Question 8

Define ionisation

Answer 8

When electrons are knocked off an atom.
Alpha = Very ionising
Beta = Medium ionisation
Gamma = Little ionisation

Question 9

Describe the penetrating ability and ionisation ability of Alpha, Beta and Gamma radiation.

Answer 9

Alpha is very ionising so loses a lot of its energy as it interacts with molecules around it and therefore does not travel very far. Gamma is the least ionising so will continue deep into objects before losing its energy. Beta is in between Alpha and Gamma.

Question 10

Describe the deflection in an electric field for Alpha, Beta and Gamma radiation.

Answer 10

Alpha - does not travel very far, gets pulled towards the positive charge.
Beta - travels further than alpha, and gets pulled towards the negative charge.
Gamma - travels further than alpha and beta, and does not get pulled to either positive nor negative charges.

Question 11

Describe the deflection in a magnetic field for Alpha, Beta and Gamma radiation.

Answer 11

Alpha - Gets pulled towards the south pole of a magnet.
Beta - Gets pulled to the north pole of a magnet.
Gamma - Does not get affected by the magnets.

Question 12

Describe half-life.

Answer 12

The half-life of an element is the average time taken for half of the radioactive nuclei of a given sample to decay
OR
The time taken for the Geiger counter count-rate to reach half the level, once background levels have been accounted for.

Question 13

Describe the safety precautions when handling radioactive materials.

Answer 13

Avoid exposure and contamination
Keep a safe distance
Limit exposure time
When handling, use gloves and tongs - do not touch the source directly.

Question 14

Describe the process of storing radioactive materials.

Answer 14

Must be stored in a container that will absorb as much radiation as possible
Containers are usually lined with lead as lead is a good absorber of all three types of radiation

Question 15

Describe the 5 uses of radioactivity.

Answer 15

Uses in medicine - Radioisotopes can be used as tracers for diagnosis or for treatments. Gamma radiation is used to kill cancerous tumours deep in the body.

Thickness control in manufacturing - Beta radiation is used to control the thickness of paper during manufacture.

Alpha source used in smoke detectors - Alpha is easily absorbed by smoke particles and the detector will signal an alarm when the radiation level drops.

Food irradiation - Gamma radiation can penetrate deep into food and kill harmful bacteria

Radiocarbon dating - The half-life of carbon-14 is 5730 years. By measuring the ratio of carbon-14 to carbon-12 we can calculate the age of organic material.