4. Atomic structure (half-life, background radiation, nuclear fission and fusion)

Question 1

What is irradiation?

Answer 1

An object that has been exposed to ioinsing radiation

Question 2

What are the uses for radiation?

Answer 2

• Producing electricty through nuclear fission
• Medical procedures including diagnosis and treatment
• Testing materials
• Determining the age of ancient artefacts
• Checking the thickness of materials
• Smoke detectors

Question 3

How are alpha particles used in smoke detectors?

Answer 3

1. Alpha particles are used in smoke detectors
2. The alpha radiation will normally ionise the air within the detector creating a current
3. The alpha emmiter is blocked when smoke enters the detector
4. The alarm is triggered by a microchip when the sensor no longer detects the alpha radiation

Question 4

How is gamma radiation used for in medical tracers?

Answer 4

1. Radioactive isotope is either injected, or swallowed into the body
2. Used as an external detector

Question 5

What is the radius of an atom?

Answer 5

Question 6

What can electrons do if the atom absorbs electromagnetic radiation?

Answer 6

Electrons can move from lower to higher energy levels

Question 7

What happens when an atom emits electromagnetic radiation?

Answer 7

The electron returns back to the lower energy levels

Question 8

What is activity?

Answer 8

The rate at which the source of an unstable nucleus decays

Question 9

What is activity measured in?

Answer 9

Bequerels

Question 10

How can you measure the activity of a radioactive source?

Answer 10

Using a gieger muller tube

Question 11

What is count rate?

Answer 11

The number of decays recorded each second by a detector

Question 12

What is ionising power?

Answer 12

When radiation collides with atoms that can cause atoms to lose electrons and form ions

Question 13

What is the half-life of a radioactive isotope?

Answer 13

The time it takes for the number of nuclei in the isotope in a sample to half

Question 14

How can you protect yourself against radiation?

Answer 14

Sheilding methods such as wearing: gloves, aprons and lead walls

Question 15

Why does the object when being sterilised with radiation not become radioactive?

Answer 15

Because the object is just exposed to radiation, it does not come into contact with the actual radioactive isotope

Question 16

What is a radiation monitor used to do?

Answer 16

It monitors how much radiation somebody has recieved. If they have recieved close to the maximum amount of radiation they can have, they will stop being exposed to it

Question 17

What is radioactive contamination?

Answer 17

When unwanted radioactive isotopes end up on other materials

Question 18

What is background radiation?

Answer 18

The radiation that is everywhere and all around us

Question 19

What are examples of natural forms of background radiation?

Answer 19

• Radioactive rocks, granite
• Cosmic rays from space

Question 20

What are examples of man made sources of background radiation?

Answer 20

• Fallout from nuclear weapons testing
• Nuclear accidents at nuclear power stations

Question 21

What is the dose of radiation measured in?

Answer 21

Sieverts

Question 22

What must radioactive tracers do/not do in order to be safe to use?

Answer 22

• They must not be strongly ionising
• They must have a short half-life
• They must emit radiation that can pass out of the body

Question 23

What is nuclear fission?

Answer 23

• In nuclear fission the nucleus of large and unstable elements (eg. uranium and plutonium) splits

Question 24

How does nuclear fission work?

Answer 24

• When a uranium nucleus absorbs a neutron this triggers the nucleus to undergo fission (split)
• When a nucleus splits it forms 2 smaller nuclei roughly equal in size
• It also emits 2 or 3 neutrons and gamma radiation
• Energy is also released during the reaction
• The neutrons emmited can now be absorbed by more uranium nuclei, triggering fission again

Question 25

What is a chain reaction?

Answer 25

When the neutrons emmited during nuclear fission is absorbed by more uranium nuclei, triggering fission again

Question 26

Where is controlled chain reactions used?

Answer 26

In a nuclear reactor

Question 27

What is nuclear fusion?

Answer 27

- When 2 light nuclei are joined to form a heavier nucleus - Some of the mass of the nuclei can be converted into energy which is released as radiation