Nuclear Physics

1. Radioactivity
 Emission of energy from unstable nuclei
which are trying to become stable
 Natural effect - radioactive isotopes are
found everywhere.
 Radiation can cause ionisation (removal
of electrons) of the atoms in our cells
which can cause mutations in DNA.

2. Radioactive Emissions
Emission What? Penetration
Alpha  2 protons
2 neutrons
few cm in air. Stopped by
paper
Beta  electron 1 metre in air. Stopped by
thin aluminium
Gamma  electromagnetic
wave
few metres of concrete will
reduce their energy.
Difficult to stop

3. Absorption of Radiation

4. Detection of Radiation
 Geiger counter
 Photographic film
 Cloud chamber

5. Background Radiation
 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

6. Uses of Radioactivity
 Treating cancer
 Internal inspection
 Tracing
 Smoke detectors
 Sterilisation
 Food irradiation
 Thickness monitoring

7. Using radioactivity
 The 3 types of radiation have different
properties.
 These properties make them useful in
different situations

8. Examples of uses.
 Smoke detectors.
 Use ALPHA
 Smoke present
Alpha Source
Detector
Alpha particles reaching the
detector - no alarm
Alpha Source
Detector
Alpha particles do not
reach the detector –
alarm goes off

9. Question.
 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
syringes.

10. RADIOACTIVITY QUIZ
Choose the correct answer …

11. 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
light.

12. 2.Which statement is false ?
A. Radiation can be used to treat cancer
B. Radiation can cause cancer
C. Cancerous cells are radioactive

13. 3.Look at the picture. The particle
labelled is:
A. An electron
B. Postively charged
C. A Gamma Ray

14. 4.Alpha particles are dangerous
because…
A. They are toxic
B. They can cause mutations of our DNA
C. They are radioactive

15. 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

16. 6.Gamma rays can be used to
sterilise food because:
A. They can kill bacteria
B. They make the food radioactive for a
short time.
C. They are very strong.

17. 7. People in Cornwall receive a higher
than average radiation dose because …
A. There are a lot of nuclear power stations in
Cornwall
B. The atmosphere is thinner there and so
there is less protection from cosmic rays.
C. There is a lot of granite underground
in Cornwall.

18. 8. Radioactive waste should be
stored in ……
A. Lead boxes
 Concrete bunkers
 It depends on the type of radiation

19. 9. Which is true?
A. Alpha particles only travel a few cm in
air
B. Alpha particles can pass through skin
C. Alpha particles are given off by
everything around us

20. 10. Which is true?
A. When something is hit by radiation it
becomes radioactive
B. Alpha and beta particles are only dangerous
if they are swallowed
C. Gamma radiation is the most penetrative.