C23Radioactivity

Why are beta-particles deflected more strongly than alpha-particles when they enter an electric field?

• Beta-particles have less mass than alpha-particles

• Beta-particles are negatively charged

• Beta-particles have lower velocities than alpha-particles

• Beta-particles have more ionising power than alpha-particles

The half-life of carbon-14 is 5700 years.

An object containing carbon-14 has a count rate of 100 counts/minute when it is first formed. The graph shows how the count rate decreases over time.

Which point on the graph corresponds to a time 11 400 years after the formation of the object?

• A

• B

• C

• D

A scientist needs to use a source of y-rays as safely as possible.

Which action will not reduce the total radiation that reaches the scientist?

• keeping the distance between the source and the scientist as large as possible

• keeping the temperature of the source as low as possible

• keeping the time for which the scientist uses the source as small as possible

• placing a lead screen between the scientist and the source

Which row correctly describes an example of radioactive decay?

• A

• B

• C

• D

What is the most effective precaution to reduce the risk when handling, storing or using a radioactive source that emits y-rays?

• Handle the source for the least possible time.

• Have a fire extinguisher nearby when using the source.

• Store the source at a low temperature.

• Wear plastic safety goggles when handling the source.

A detector is used to monitor the emissions from a radioactive source over several days.

The table shows the count rate from the source at different times.

What is the half-life of the source?

• between 1 and 2 days

• between 2 and 3 days

• between 3 and 4 days

• between 4 and 5 days

Radioisotope X decays to the stable isotope Y. The graph shows how the mass of Y present in a sample varies with time.

Which time interval gives the half-life of X?

• t2-t1

• t3-t2

• t2

• 0.5 t3

a-particles, B-particles and y-rays are emitted by radioactive nuclei when they decay.

Which emissions can be deflected by an electric field?

• a-particles, ẞ-particles and y-rays

• α-particles and B-particles only

• B-particles and y-rays only

• y-rays and a-particles only

A scientist carries out an experiment using a sealed source which emits ẞ-particles. The range of the B-particles in the air is about 30 cm.

Which precaution is the most effective to protect the scientist from the radiation?

• handling the source with long tongs

• keeping the temperature of the source low

• opening all windows in the laboratory

• washing his hands before leaving the laboratory

The graph shows the count rate from a radioactive source over a period of time

What is the half-life of the source?

• 0.5 hours

• 1.0 hours

• 1.5 hours

• 3.0 hours