Radiation

Question 1

What is meant by ‘ionising radiation’ ?

Answer 1

Ionising radiation causes electrons to removed from an atom (or molecule).

Question 2

What is meant by absorbed dose?

Answer 2

Absorbed dose is the energy absorbed per kilogram (of material).

• Ionising radiation carries energy.
• This energy can be absorbed by tissue and cause damage.
• If the energy is concentrated on a small mass, the absorbed dose is greater.

Question 3

What does the prefix n stand for?

Answer 3

n stands for nano

nano = x 10^-9

Question 4

What does the prefix m stand for?

Answer 4

m stands for milli

milli = x 10^-3

Question 5

List some applications of nuclear radiation.

(at least three)

Answer 5

• chemical tracers to help with medical diagnosis
• killing cancer cells
• sterilising medical instruments
• measuring thickness of materials
• carbon dating
• smoke detectors

Question 6

What are the three main forms of protection against the effects of radiation?

Answer 6

Time

(the amount of time spent near a source of radiation affects the exposure)

Distance

(the greater the distance from the radiation source, the lower the exposure)

Shielding

(certain materials can limit the exposure to radiation)

Question 7

What is the radiation weighting factor?

Answer 7

The radiation weighting factor is a number that takes into account the type of radiation to which you are exposed.

Question 8

What does the prefix G stand for?

Answer 8

G stands for giga

giga = x 10⁹

Question 9

Name the three quantities shown in this formula.

Answer 9

A = activity

N = number of decays

t = time

Question 10

What is the unit for energy?

Answer 10

The unit for energy is joules (J)

Question 11

What is meant by half-life of a radioactive source?

Answer 11

The time taken for half the nuclei in a radioactive sample to decay

OR

The time taken for the activity of a radioactive sample to fall by half its original value

Question 12

Name the three quantities shown in this formula.

Answer 12

D = absorbed dose

E = energy

m = mass

Question 13

What is the charge on a gamma ray?

Answer 13

A gamma ray has no charge - it is a wave, not a particle.

Question 14

Describe the materials which can be used to block/absorb the three types of nuclear radiation.

Answer 14

Alpha - paper or a few cm of air

Beta - thin sheet of aluminium

Gamma - a few cm of lead or thick concrete

Question 15

A radioactive source has an activity of 64 MBq (mega becquerels), and a half-life of 2 hours.

What will be the activity of the source after 8 hours?

Answer 15

The activity will be 4 MBq.

Every half-life, the activity falls by half:

Start 64 MBq

2 hours 32 MBq

4 hours 16 MBq

6 hours 8 MBq

8 hours 4 MBq

Question 16

What is meant by fusion?

Answer 16

Fusion involves two nuclei joining together to make a large nucleus

Question 17

What is the charge on an alpha particle?

Answer 17

An alpha particle has a positive charge.

Question 18

What is the unit for mass?

Answer 18

The unit for mass is kilograms (kg)

Question 19

What is meant by background radiation?

Answer 19

• Background radiation is produced around us all the time: sources include
• certain rocks
• cosmic radiation (from space)
• radon gas in the air
• nuclear waste
• medical applications
• some foods

Question 20

State a source of man-made (artificial) background radiation.

Answer 20

Sources of man-made background radiation include:

• weapons testing
• waste from nuclear industry
• medical uses (X-ray, CT scan…)

Question 21

What is the unit for radiation weighting factor, w_R ?

Answer 21

There are no units for radiation weighting factor, w_R - it’s just a number

Question 22

What is meant by fission?

Answer 22

Fission means the splitting of a nucleus.

• Normally, fission is carried out with uranium or plutonium
• Fission can be spontaneous (happens randomly) or induced (caused by firing a neutron at a nucleus)
• The nucleus splits into two smaller nuclei
• 2 or 3 more neutrons are released
• Energy is released

Question 23

What does the prefix µ stand for?

Answer 23

µ stands for micro

micro = x 10^-6

Question 24

What does the prefix M stand for?

Answer 24

M stands for mega

mega = x 10⁶

Question 25

Which is the most strongly ionising radiation?

Answer 25

Alpha radiation is the most strongly ionising.

Question 26

Describe what is meant by alpha radiation.

Answer 26

• Alpha radiation is a particle
• It is relatively slow and heavy
• It is made up of 2 protons and 2 neutrons
• It is positively charged

Question 27

Name the three types of nuclear radiation.

Answer 27

Alpha α

Beta β

Gamma γ

Question 28

Describe what is meant by gamma radiation.

Answer 28

• Gamma radiation is a wave in the electromagnetic spectrum
• Gamma rays have no mass or charge
• Gamma rays have a very short wavelength and a high frequency

Question 29

What is meant by the activity of a radioactive source?

Answer 29

Activity of a source is the number of decays per second.

Question 30

What is the unit for equivalent dose?

Answer 30

The unit for equivalent dose is sieverts (Sv)

Question 31

What is the unit for absorbed dose?

Answer 31

The unit for absorbed dose is grays (Gy)

Question 32

What is the charge on a beta particle?

Answer 32

A beta particle has a negative charge.

Question 33

What does the prefix k stand for?

Answer 33

k stands for kilo

kilo = x 10³

Question 34

Describe what is meant by beta radiation.

Answer 34

• Beta radiation is a particle
• It is the same as an electron - a beta particle is negatively charged
• It is relatively fast and light

Question 35

What is meant by equivalent dose?

Answer 35

Equivalent dose measures the biological effects of ionising radiations.

It takes into account the type of radiation, the energy carried by the radiation, and how much tissue absorbs the energy.

Question 36

What is the unit for time?

Answer 36

The unit for time is seconds (s)

Question 37

What is the unit for activity?

(of a radioactive source)

Answer 37

The unit for activity is becquerels (Bq)

Question 38

Name the three quantities shown in this formula.

Answer 38

H = equivalent dose

D = absorbed dose

w_R = radiation weighting factor

Question 39

State a source of natural background radiation.

Answer 39

Sources of natural background radiation include:

• rocks
• food
• human body
• cosmic rays (radiation from Sun and outer space)
• radon gas in the atmosphere