• Emission of energy from unstable nuclei
which are trying to become stable
• Natural effect - radioactive isotopes are
• Radiation can cause ionisation (removal
of electrons) of the atoms in our cells
which can cause mutations in DNA.
Emission What? Penetration
few cm in air. Stopped by
Beta β electron 1 metre in air. Stopped by
Gamma γ electromagnetic
few metres of concrete will
reduce their energy.
Difficult to stop
Absorption of Radiation
Detection of Radiation
• Geiger counter
• Photographic film
• Cloud chamber
• Radioactive isotopes occur naturally:
Cosmic rays – we are protected from these by the
atmosphere, but airline pilots receive a higher dose.
Granite – contains uranium, people in Cornwall receive a
higher dose than usual because there is a lot of granite there.
Food, our bodies, buildings etc.
• There are also made artificially:
Medical Uses – cancer treatment, medical tracers
Nuclear Industry – weapons industry, power industry
Uses of Radioactivity
• Treating cancer
• Internal inspection
• Smoke detectors
• Food irradiation
• Thickness monitoring
• The 3 types of radiation have different
• These properties make them useful in
Examples of uses.
• Smoke detectors.
• Use ALPHA
• Smoke present
Alpha particles reaching the
detector - no alarm
Alpha particles do not
reach the detector –
alarm goes off
• Why would Beta or Gamma radiation not
be suitable in a smoke detector?
• Which radiation would be most suitable
for internal inspection of jet engines?
• How is gamma used for sterilising
Choose the correct answer …
1.Which statement is TRUE ?
A. Alpha particles have a positive charge
B. An alpha particle is an electron
C. Alpha particles travel at the speed of
2.Which statement is false ?
A. Radiation can be used to treat cancer
B. Radiation can cause cancer
C. Cancerous cells are radioactive
3.Look at the picture. The particle
A. An electron
B. Postively charged
C. A Gamma Ray
4.Alpha particles are dangerous
A. They are toxic
B. They can cause mutations of our DNA
C. They are radioactive
5.Gamma radiation …
A. Is a stream of particles called electrons
B. Travels at the speed of light
C. Can be stopped by 3 mm of aluminium
6.Gamma rays can be used to
sterilise food because:
A. They can kill bacteria
B. They make the food radioactive for a
C. They are very strong.
7. People in Cornwall receive a higher
than average radiation dose because …
A. There are a lot of nuclear power stations in
B. The atmosphere is thinner there and so
there is less protection from cosmic rays.
C. There is a lot of granite underground
8. Radioactive waste should be
stored in ……
A. Lead boxes
• Concrete bunkers
• It depends on the type of radiation
9. Which is true?
A. Alpha particles only travel a few cm in
B. Alpha particles can pass through skin
C. Alpha particles are given off by
everything around us
10. Which is true?
A. When something is hit by radiation it
B. Alpha and beta particles are only dangerous
if they are swallowed
C. Gamma radiation is the most penetrative.