Grade 12 Radioactivity

What did Henri Becquerel first use to detect ionising radiation being emitted from uranium ore?

• photographic film

• a spark counter

• a Geiger–Müller tube

• a metal plate

A Geiger–Müller tube can be used to detect ionising radiation. The tube is filled with low pressure gas. How does this detect ionising radiation?

• The gas lights up when hit with ionising radiation.

• The gas becomes ionised and a current flow occurs inside the tube.

• The gas does not react.

• None of the above.

Which of the following is the biggest contributor to background radiation?

• nuclear power

• food and drink

• radon gas

• medical devices

Where is radon gas released from mainly?

• the oceans

• outer space

• rocks

• humans

On Earth we receive low levels of radiation from outer space. What protects us from receiving higher doses of radiation from outer space?

• the Sun

• the Moon

• the oceans

• the atmosphere

Which of the following correctly describes the meaning of the term half-life?

• the amount of time it takes for the activity of a substance to halve

• the amount of time it takes for the number of undecayed atoms to halve

• the amount of time it takes the mass of a radioactive substance to halve

• all of the above

Radioactive decay is described as what sort of process?

• a random process

• an ordered process

• an unknown process

• an easy process

The graph shows the decay of an unknown substance X. What is the half-life of substance X?

• 5 days

• 1 day

• 2 days

• 40 days

Substance X undergoes three half-lives. What is the count rate of substance X at this time?

• 10 counts per minute

• 40 counts per minute

• 80 counts per minute

• 60 counts per minute

When determining the activity of a sample, a corrected count rate is used. What is meant by the term corrected count rate?

• The count rate is corrected to a new value when the answer does not look right.

• The background count rate is subtracted from the sample’s recorded count rate.

• The background count rate is added to the sample’s recorded count rate.

• All the values are double checked with known samples and adjusted so they fit other samples’ results.