A geologist measures the activity of a radioactive mineral specimen using a Geiger-Müller tube and counter.

First, they measure the background radiation count rate when the mineral specimen is not present. Then, they measure the total count rate with the mineral specimen in place.

The table shows the geologist's results:

$\begin{array}{lc}Measurement& Count\; rate\; (cpm)\\ Background\; radiation\; only& 36\\ With\; mineral\; specimen\; present& 1596\end{array}$

How can the geologist determine the actual activity due only to the mineral specimen?

Tick ($✓$) one box.

• Add the background count rate to the measured count rate.
• Subtract the background count rate from the measured count rate.
• Multiply the measured count rate by the background count rate.
• Divide the measured count rate by the background count rate.

Calculate the actual activity of the mineral specimen in counts per second (cps).

Activity = $\dots \dots \dots \dots \dots$ counts per second

Technetium-99m is a radioactive isotope used as a medical tracer in diagnostic imaging.

Technetium-99m has a relatively short half-life of 6 hours. Explain why a short half-life is important for the patient.

Using Technetium-99m for bone scans exposes the patient to ionizing radiation, which carries a small risk of cell damage, and requires precautions like drinking extra fluids to flush the isotope out. Explain why patients are still scanned with Technetium-99m despite these risks.