Measuring radioactivity

Question 1

two ways to measure and detect radiation

Answer 1

photographic film and a Geiger-Müller tube

Question 2

how does a Geiger-Müller tube work? (4)

Answer 2

• the GM tube contains argon gas, when radiation enters the tube the atoms are ionised and electrons travel towards a thin wire
• it contains a thin wire in the middle that is connected to a power supply
• when electrons travel down the thin wire, more electrons are knocked from atoms, causing a chain reaction
• the amount of radiation detected is then shown by the counter/ratemeter attached

Question 3

What is radiation measured in?

Answer 3

electron volts or joules

Question 4

what effect does radiation have on photographic film?

Answer 4

it darkens it

Question 5

what is the purpose of a film badge?

Answer 5

detects if and what type of radiation workers in a possibly radioactive area are exposed to

Question 6

basic layout of a film badge/dosimeter

Answer 6

• contains photographic film
• different sections to detect different types of radiation
• thin and thick windows of plastic/aluminium
• open window
• lead between the plastic case and the film

Question 7

why is a film badge needed?

Answer 7

it is a way to monitor how much/what types of radiation someone is exposed to, as too much is dangerous

Question 8

Explain why there is an open window in the film badge [3]

Answer 8

light rays will darken the film
since the film badge is designed to detect nuclear radiation, this acts as a control so that you know the film is working

Question 9

Explain why the film badge has aluminium and lead sheets inserted in it [3]

Answer 9

aluminium absorbs beta particles and lead absorbs gamma rays

is there is darkening behind these sheets, then high energy beta/gamma rays may have gotten through and so the nature of the radiation can be determined and the risk identified

Question 10

Explain why GM tubes are better at detecting alpha particles than beta/gamma rays [3]

Answer 10

alpha particles are more ionising than gamma and beta radiation so more electrons are released per collision, so the current is greater and therefore easier to detect

Question 11

Explain how a film from a film badge would tell you if there was a potential risk to humans [3]

Answer 11

if the film behind the plastic and lead is darkened then radiation has reached it

gamma rays have been detected and the person is at risk as these are dangerous outside the body and can lead to cellular mutations/cancer/death