Radioactivity

Question 1

How is Alpha, Beta and Gamma radiation emitted

Answer 1

• In alpha and beta, a charged particle is emitted from the
  the nucleus, in gamma, an electromagnetic wave is emitted.
• Neutron heavy nuclei emit negative beta particles
• Neutron light nuclei emit positive beta particles
• The heaviest element amit alpha particles
• Any sufficiently energetic nuclei can emit gamma

Question 2

Describe what happens when Alpha radiation is emitted.

Answer 2

• Very heavy, around 7300 times the mass of a beta particle
• When an alpha particle is emitted, the atomic number of the
  emitting nucleus drops by 2 and the mass number by 4. This
  causes the atomic nucleus to be transmuted into the nucleus
  of another element.
• When emitted from an atomic nucleus, the alpha particle is
  travelling at about 10% of the speed of light.
• Large amount of kinetic energy (5 megaelectron volts)
• Very ionising

Question 3

Describe Beta radiation

Answer 3

• Charge of -1 or +1

Question 4

Describe Gamma radiation

Answer 4

• No charge

- No mass

Question 5

Describe Alpha radiation.

Answer 5

• An alpha particle is composed of 2 neutrons and 2 protons
  bound together. Identical to the nucleus of a helium atom.
• Charge of +2

Question 6

How does ionisation cause cancer?

Answer 6

Alpha particles have the most energy and are therefore the most ionising. They’re so energetic that they can knock the electrons orbiting atoms out of place, causing the atoms to become ionised - to become charged. This ionisation effect can damage fragile molecules like DNA and this can cause cells to reproduce incorrectly. This can lead to cancer.

Question 7

Name three sources of background radiation

Answer 7

Rocks (Radon gas - Alpha)
Food
Nuclear power station (man-made example)

Question 8

Explain how to accurately measure the radioactivity of a sample

Answer 8

Use GM tube to take multiple readings of background radiation in different locations

Find average background radiation count

Place a radioactive sample near GM tube and take reading
Subtract background radiation from reading

(To work out how far the radiation travels - keep moving GM tube away from source until levels match background radiation levels)

Question 9

Describe three safety measures when handling radioactive source

Answer 9

Keep radioactive source facing away from you
Limit exposure time
Store in a lead-lined container