A researcher investigates the types of radiation emitted by three radioactive sources, P, Q, and R. She does this by measuring the amount of radiation (the count) received by a detector.
She uses the following method:
The researcher then measures the count for each source again, placing paper, aluminium, and lead as absorbing materials between the source and the detector.
State two pieces of laboratory apparatus required to measure the count rate in this procedure.
Table 1 shows the results of the researcher's investigation.
Table 1
| Count with no absorber | Count with paper | Count with aluminium | Count with lead | |
|---|---|---|---|---|
| Source P | 15000 | 4200 | 4180 | 40 |
| Source Q | 3100 | 3085 | 45 | 42 |
| Source R | 9800 | 3400 | 45 | 42 |
Copy and complete the table below by ticking (✓\checkmark✓) the boxes to show which types of radiation are emitted by each source.
| Alpha | Beta | Gamma | |
|---|---|---|---|
| Source P | |||
| Source Q | |||
| Source R |
Suggest why there is still a count recorded for each source, even when lead is used as an absorbing material.
A different radioactive isotope, Isotope S, has a half-life of 8 hours8\text{ hours}8 hours.
State what is meant by the term half-life.
The initial count rate for Isotope S is 1200 counts per second1200\text{ counts per second}1200 counts per second. Calculate how many hours it will take for the count rate for Isotope S to fall below 100 counts per second100\text{ counts per second}100 counts per second.
