Hospitals use ionising radiation for many purposes - Edexcel - GCSE Physics - Question 6 - 2015 - Paper 1

To determine the amount of technicium-99 remaining after 12 hours, we first calculate how many half-lives have passed. Given that the half-life of technicium-99 is 6 hours, after 12 hours (which is 2 half-lives), we can calculate:

1. After the first half-life (6 hours), the amount remaining is:

   $40 ext{ mg} imes \frac{1}{2} = 20 ext{ mg}$

2. After the second half-life (another 6 hours), the amount is:

   $20 ext{ mg} \times \frac{1}{2} = 10 ext{ mg}$

Thus, after 12 hours, the amount of technicium-99 remaining is 10 mg.

It is important to monitor the amount of radiation a radiographer absorbs each month because:

1. Health Risks: Excessive exposure to radiation can cause harmful effects, such as cancer or tissue damage. Monitoring ensures that the exposure levels remain within safe limits.

2. Compliance: Regulatory bodies often set standards for radiation exposure. Monitoring helps ensure compliance with these regulations, ensuring the safety of radiographers.

The correct answer is C: we have a better understanding of the risks from radiation. This reflects advancements in safety knowledge and practices.