Radiation

Question 1

What is radioactive decay?

Answer 1

When nuclear radiation is emitted by unstable atomic nuclei to become more stable.

Question 2

What sort of process is radioactive decay?

Answer 2

Random

Question 3

What is ionisation?

Answer 3

When radioactive decay causes electrons to be expelled from atoms

Question 4

What is an alpha particle?

Answer 4

Two protons, two neutrons

Question 5

What happens to the nucleus when an alpha particle is expelled?

Answer 5

Loses 2 protons and 2 neutrons

Question 6

What is the ionising power of alpha particles?

Answer 6

Highest

Question 7

What is the range of alpha particles?

Answer 7

Travels a few cm in air

Question 8

What are alpha particles stopped by?

Answer 8

A sheet of paper

Question 9

What are beta particles?

Answer 9

Fast moving electrons

Question 10

What happens to the nucleus when a beta particle is expelled?

Answer 10

A neutron becomes a proton and an electron

Question 11

What is the ionising power of beta particles?

Answer 11

High

Question 12

What is the range of beta particles?

Answer 12

Travels ~1m in air

Question 13

What are beta particles stopped by?

Answer 13

A few mm of a aluminium

Question 14

What is gamma radiation?

Answer 14

Short wavelength, high frequency EM radiation

Question 15

What happens to the nucleus when gamma radiation is expelled?

Answer 15

Energy is transferred away from nucleus

Question 16

What is the ionising power of gamma radiation?

Answer 16

Low ionising power

Question 17

What is the range of gamma radiation?

Answer 17

Virtually unlimited range in air

Question 18

What is gamma radiation stopped by?

Answer 18

Several cm of thick lead, metres of concrete

Question 19

What is the decay equation for an alpha particle?

Answer 19

A,ZX -> (A-4),(Z-2)Y + 4,2α

Question 20

What is the decay equation for a beta particle?

Answer 20

A,ZX -> A,(Z+1)Y + 0,-1β

Question 21

What is the decay equation for gamma radiation?

Answer 21

A,ZX -> A,ZX + 00γ

Question 22

What is activity?

Answer 22

The rate of decay of an unstable nucleus

Question 23

What is activity measured in?

Answer 23

Bq (becquerel)

Question 24

What is count rate?

Answer 24

The number of decays detected per second

Question 25

How do we calculate count rate?

Answer 25

Count rate after n half-lives = initial count rate/2ⁿ

Question 26

What is half life?

Answer 26

The time it takes for: 1. Half the number of unstable nuclei in a sample to decay 2. Cours rate or activity of a source to halve

Question 27

How do you calculate net decline?

Answer 27

Reduction in activity/original activity

Question 28

What is irradiation?

Answer 28

When an object is exposed to nuclear radiation

Question 29

What is contamination?

Answer 29

When atoms of a radioactive material are in or on an object

Question 30

How can you prevent irradiation?

Answer 30

Shielding, removing, moving away from source of radiation

Question 31

How can you remove contamination?

Answer 31

It is very hard to remove - object remains exposed to radiation as long as it is contaminated

Question 32

How can we protect against irradiation and contamination?

Answer 32

1. Maintain distance from radiation source 2. Limit time near source 3. Shielding from radiation

Question 33

What should be done on all studies of radiation published?

Answer 33

Peer review

Question 34

Why is ionising radiation dangerous?

Answer 34

Can kill or damage living cells

Question 35

What does the risk of a radioactive source depend on?

Answer 35

Its half-life, type of radiation

Question 36

Why is alpha radiation more dangerous inside the body than on the outside?

Answer 36

Inside: affects all surrounding tissue Outside: only affects skin and eyes as cannot penetrate further

Question 37

What is radiation dose?

Answer 37

Measure of health risk of exposure to radiation

Question 38

What is radiation dose measured in?

Answer 38

Sieverts (Sv)

Question 39

What is background radiation?

Answer 39

Radiation around us all the time

Question 40

Where does background radiation come from?

Answer 40

1. Natural sources (rocks, cosmic rays) 2. Nuclear weapons, accidents

Question 41

Name 2 ways nuclear radiation is used in medicine.

Answer 41

1. Tracers 2. Control or destruction of unwanted tissue (e.g: tumours)

Question 42

How are tracers used in medicine?

Answer 42

1. Gamma-emitting tracers injected or swallowed by patient 2. Gamma cameras create image showing path of tracer

Question 43

Why must the half life of a tracer be short?

Answer 43

So most nuclei will decay shortly after image is taken -> limit *reaction dose*

Question 44

Describe 1 way radiation is used to control/destroy unwanted tissue.

Answer 44

Narrow beams of gamma radiation focused on tumour cells to destroy them.

Question 45

Why is gamma radiation used to destroy tumour cells?

Answer 45

Can penetrate from outside body - high penetrative ability

Question 46

Describe another way radiation is used to control or destroy unwanted tissue.

Answer 46

Beta or gamma-emitting implants surgically placed inside/next to tumours

Question 47

Why is the half life of beta/gamma-emitting implants important?

Answer 47

Half lives must be long enough to be effective, but short enough to not irradiate patient after treatment.

Question 48

What is nuclear fission?

Answer 48

When a large, unstable nucleus absorbs an *extra neutron*, then *divides into two smaller nuclei.*

Question 49

What happens during nuclear fission?

Answer 49

1. Gamma radiation emitted and energy released 2. 2-3 neutron emitted -> can cause chain reaction

Question 50

How are chain reactions in power stations controlled?

Answer 50

Absorbing neutrons

Question 51

What are nuclear explosions?

Answer 51

Uncontrolled chain reactions

Question 52

What is spontaneous fission?

Answer 52

When an unstable nucleus splits apart *without* absorbing a neutron