Radioactivity - ESA

Radioactivity - ESA


• 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.

Radioactive Emissions

Emission What? Penetration

Alpha α

2 protons

2 neutrons

few cm in air. Stopped by


Beta β electron 1 metre in air. Stopped by

thin aluminium

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

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

Uses of Radioactivity

• Treating cancer

• Internal inspection

• Tracing

• Smoke detectors

• Sterilisation

• Food irradiation

• Thickness monitoring

Using radioactivity

• The 3 types of radiation have different


• These properties make them useful in

different situations

Examples of uses.

• Smoke detectors.


Alpha Source

• Smoke present

Alpha Source


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

labelled is:

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

short time.

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

in Cornwall.

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

becomes radioactive

B. Alpha and beta particles are only dangerous

if they are swallowed

C. Gamma radiation is the most penetrative.

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