Topic 4

Question 1

What are isotope of an element?

Answer 1

Atoms with the same number of protons but but q different number of neutrons

Question 2

Why do radioactive substances release atoms when they decay?

Answer 2

To rebalance their atomic and mass number

Question 3

What is ionising radiation and ionising power of a radiation source?

Answer 3

Ionising radiation is radiation that knocks electrons off atoms creating positive ions. The ionising power of a radiation source is how easily it can do this.

Question 4

Where is alpha radiation emitted from and what does an alpha particle consist of?

Answer 4

Alpha radiation is emitted from the nucleus. An alpha particle is two neutrons and two protons (like a helium neuclus)

Question 5

How far can alpha particles penetrate material?

Answer 5

They don’t penetrate very far into materials and are stopped quickly - they can only travel a few cm in the air

Question 6

How ionising are alpha particles?

Answer 6

Because of their size they are strongly ionising

Question 7

What is a beta particle?

Answer 7

a beta particle is simply a fast moving electron released by the nucleus

Question 8

What is the charge of the beta particle?

Answer 8

-1

Question 9

How ionising are beta particles?

Answer 9

moderately ionising

Question 10

How far can beta particles penetrate material?

Answer 10

They penetrate moderately far into materials before colliding and have a range in air of a few metres.

Question 11

What is are beta particles absorbed by?

Answer 11

sheet of aluminium (around 5mm)

Question 12

What happens in the nucleus when a beta particle is emitted?

Answer 12

a neuron in the nucleus has turned into a proton.

Question 13

What are gamma rays?

Answer 13

Gamma rays are waves of electromagnetic radiation released by the nucleus.

Question 14

How far can gamma rays penetrate material?

Answer 14

They penetrate far into materials without being stopped and will travel a long distance through air

Question 15

How ionising are gamma rays?

Answer 15

weakly ionising because they tend to pass through rather than collide with atoms.

Question 16

What is are gamma rays absorbed by?

Answer 16

lead or metres of concrete

Question 17

What form are nuclear equations written in?

Answer 17

atom before decay —> atom after decay + radiation emitted

Question 18

What has to be balanced on both sides in a nuclear equation?

Answer 18

mass and atomic number

Question 19

What does alpha decay do to a nucleus?

Answer 19

Alpha decay decreases the charge and mass of the nucleus

Question 20

How can an alpha particle be written?

Answer 20

as a helium nucleus 4
He
2

Question 21

What does beta decay do to a nucleus?

Answer 21

Beta decay decreases the charge of the nucleus

Question 22

What happens to the particles in the nucleus when beta decay occurs?

Answer 22

A neutron in the nucleus turns into a proton and releases a fast-moving electron (the beta nucleus) because the nucleus has lost a neutron and gained a proton during beta decay, the mass of the nucleus doesn’t change.

Question 23

How can an beta particle be written?

Answer 23

beta particles can be written as 0
e
-1

Question 24

How do gamma rays effect the nucleus?

Answer 24

gamma rays don’t change the charge or mass of the nucleus

Question 25

What do gamma rays do in the nucleus?

Answer 25

Gamma rays are a way of getting rid of excess energy from a nucleus. This means that there is no charge to the atomic mass or atomic number of the atom

Question 26

What kind of process is radioactivity?

Answer 26

radioactivity is a totally random process

Question 27

Where do radioactive substances give out radiation from?

Answer 27

Radioactive substances give out radiation from the nuclei of their atoms

Question 28

How can radiation be measured?

Answer 28

Geiger-Muller tube and counter

Question 29

What can the half-life be used for?

Answer 29

to find the rate at which a source decays

Question 30

What is a source that decays activity measured in?

Answer 30

Becquerels, Bq where 1 Bq is 1 decay per second

Question 31

Why does a radioactive nucleus decay?

Answer 31

to become a stable nucleus

Question 32

What happens every time a radioactive nucleus decays to become stable?

Answer 32

the activity as a whole will decrease

Question 33

What is the problem with trying to measure the activity of a radioactive source?

Answer 33

that the activity never reaches 0, which is why we have to use the idea of half-life to measure how quickly the activity drops

Question 34

What is the half-life?

Answer 34

The half-life is the time taken for the number of radioactive nuclei in an isotope to halve. It is also the time taken for the activity and so count-rate to halve.

Question 35

What does a short half-life mean?

Answer 35

A short half-life means the activity falls quickly because the nuclei are very unstable and rapidly decay.

Question 36

Are sources with a short half-life safe?

Answer 36

Sources with a short half-life are dangerous because of the high amount of radiation they emit at the start but they quickly become safe.

Question 37

What does a long half-life mean?

Answer 37

A long half-life means the activity falls more slowly because most of the nuclei don't decay for a long time so the source just sits there, releasing small amounts of radiation for a long time.

Question 38

Are sources with a long half-life safe?

Answer 38

Sources with long half-life's can be dangerous because nearby areas are exposed to radiation for (millions of) years.

Question 39

What is background radiation?

Answer 39

Background radiation is the low-level radiation that's around us all the time. You should always measure and subtract the background radiation from your results (to avoid systematic error).

Question 40

What does background radiation come from?

Answer 40

-Radioactivity of naturally occurring unstable isotopes which are all around us -Radiation from space, which is known as cosmic rays. These come mostly from the sun. Luckily, the earths atmosphere protects us from most of this radiation. -Radiation due to human activity e.g. fallout from nuclear explosions or nuclear waste

Question 41

What does the dose of radiation tell you?

Answer 41

the risk of harm to body tissues due to exposure to radiation

Question 42

What is radiation measured in?

Answer 42

sieverts (sv)

Question 43

Convert 1 sievert to millisieverts.

Answer 43

1Sv = 1000mSv

Question 44

What is irradiation?

Answer 44

exposure to radiation

Question 45

What can you do to reduce the effects of irradiation?

Answer 45

-keeping sources in led boxes -standing behind barries -being in different rooms

Question 46

What is contamination?

Answer 46

when unwanted radioactive atoms get onto or into an object

Question 47

What can happen to contaminated atoms?

Answer 47

they might decay, releasing radiation which could cause you harm

Question 48

Why is contamination dangerous?

Answer 48

because radioactive particles could get inside your body

Question 49

What should you to when handling contaminated sources and why?

Answer 49

gloves and tongs should be used when handling contaminated sources, to avoid particles getting stuck to your skin or under your nails. Some industrial workers wear protective suits to stop them breathing in particles

Question 50

Outside the body what are the most dangerous sources and why?

Answer 50

Outside the body, beta and gamma sources are the most dangerous because beta and gamma can penetrate the body and get to the delicate organs. Alpha is less dangerous because it can't penetrate the skin and is easily blocked by small air gaps.

Question 51

Inside the body what are the most dangerous sources and why?

Answer 51

Inside the body, alpha sources are the most dangerous because they do all their damage in a very localised area. So contamination, rather then irradiation is the major concern when working with alpha sources.

Question 52

Why are betta and gamma sources less damaging inside the body?

Answer 52

Betta sources are less damaging inside the body as radiation is absorbed over a wider area and some passes out the body all together. Gamma sources are less dangerous inside the body as they mostly pass straight through - they have the lowest ionising power.