P7 - (Part 2) Radioactivity

Question 1

What is radioactive decay

Answer 1

• Where an unstable nucleus give out ionsing radiation to become more stable over time
• This is a random process so you can’t predict when a particular nucleus will decay

Question 2

What is meant by the activity of a radioactive substance

Answer 2

The rate of which unstable nuclei decay
This is measured in becquerel (Bq)

1Bq = 1 decay per second

Question 3

4 Different types of radiaiton that can be given off

Answer 3

• Alpha
• Beta
• Gamma rays
• A neutron

Question 4

What is an alpha radiation particle

Answer 4

The same as a helium nucleus (2 protons 2 neutrons)

Question 5

What is a beta radiaiton particle

Answer 5

A high speed electron ejected from the nucleus
It is formed when a neutron changes into a proton and an electron

Question 6

Properties of alpha radiation

Answer 6

• Short range in air (<5cm)
• Weak penetrating power - stopped by a sheet of paper
• Highly ionising

Question 7

Properties of beta radiation

Answer 7

• medium range in air (<1m)
• medium penetrating power - stopped by a sheet of aluminium
• Quite highly ionising

Question 8

Properties of gamma radiation

Answer 8

• Very long range in air
• High penetrating power - stopped by several cm of lead
• Weakly ionising

Question 9

What is the half life of a radioactive isotope

Answer 9

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

Also can be defined as the time it takes for the count rate/activity to fall to half its initial value

Question 10

What is irradiation and how can it be used

Answer 10

Exposing an object to nuclear radiation but the object doesn’t become radioactive itself
It is used to sterlise things such as surgery equipment

Question 11

Precautions used when handling radiation

Answer 11

• Shielding such as gloves, lead aprons or lead screens
• Monitoring - stops someone from being around radiation for too long

Question 12

What is radioactive contamination

Answer 12

• When unwanted radioactive isotopes end up on other materials
• This causes the atoms to decay and emit ionising radiaiton

Question 13

Natural sources of background radiation

Answer 13

• Radioactive rocks such as granite
• Cosmic rays from space such as from exploding stars

Question 14

Man made sources of background radiation

Answer 14

• Fallout from nuclear weapon testing
• Nuclear accidents

Question 15

How can radiation be used in medicine

Answer 15

• Used as tracers to detect problems in the body
• Destroying cancer cells trhough radiotherapy - also destroys healthy tissue

Question 16

Properties of a tracer radiation source

Answer 16

• High penetrating power so can be detected outside the body
• Not strongly ionising
• Short half life
• Musn’t decay into another radioactive isotope

Question 17

What happens in nuclear fission

Answer 17

• Large nuclues splits into smaller daughter nuclei when it absorbs a fission neutron
• Gamma radiation, energy and other fission neutrons are released
• Neutrons absorbed by other unstable nuclei triggering more fission
• This is a chain reaction and can be controlled to produce energy in a nuclear reactor

Can also be uncontrolled as in a nuclear weapon

Question 18

What happens in nuclear fusion

Answer 18

• Two small light nuclei join together to form a larger, heavier nucleus
• Some of the mass is converted into energy released as radiaition

Happens in stars

Question 19

Conditions required for nuclear fusion

Answer 19

• High temp - overcome repulsion
• High pressure - makes nuclei close together