An experimental physicist is testing the shielding properties of various materials against radioactive emissions. A Geiger-Müller (GM) tube is positioned at a fixed distance of 1.5 cm1.5\text{ cm}1.5 cm from a sample holder. For each test, the total count is recorded over a duration of 100 s100\text{ s}100 s.
The table below shows the results of the experiment:
| Radiation Source | Count in 100 s100\text{ s}100 s (no absorber) | Count in 100 s100\text{ s}100 s (0.1 mm0.1\text{ mm}0.1 mm paper) | Count in 100 s100\text{ s}100 s (3 mm3\text{ mm}3 mm aluminium) | Count in 100 s100\text{ s}100 s (10 mm10\text{ mm}10 mm lead) |
|---|---|---|---|---|
| Source P | 15400 | 46 | 44 | 45 |
| Source Q | 9800 | 9750 | 48 | 44 |
| None | 45 | 44 | 46 | 43 |
Explain why a non-zero count is recorded even when no radiation source is present.
State the physical reason why the student must maintain the distance between the source and the GM tube at a constant value of 1.5 cm1.5\text{ cm}1.5 cm throughout all trials.
Using the data provided in the table, identify and explain the type of radiation emitted by: (i) Source Q
(ii) Source P
