A student watches a radioactivity demonstration - Edexcel - GCSE Physics - Question 2 - 2012 - Paper 1

The box is lined with lead to effectively shield against radiation. Lead is dense and can absorb alpha particles and other forms of radiation, thereby preventing them from escaping and ensuring safety.

One source of background radiation is cosmic rays from outer space.

1. Maintain a safe distance between the students and the radioactive source to minimize exposure.

2. Use protective clothing and ensure that the class does not consume food or drink during the demonstration to avoid contamination.

To calculate the mass remaining after 8 days, we first need to determine the number of half-lives that have passed.

The half-life of radon is 4 days. In 8 days, there are:

$ext{Number of half-lives} = \frac{8}{4} = 2$

Starting with 6 mg of radon, after each half-life, the mass is halved:

1st half-life: $6 \text{ mg} \div 2 = 3 \text{ mg}$

2nd half-life: $3 \text{ mg} \div 2 = 1.5 \text{ mg}$

So, the mass remaining after 8 days is 1.5 mg.

People living in areas with rocks that release radon gas are at an increased risk of long-term health problems because radon is a known carcinogen. Prolonged exposure to radon can lead to lung cancer, especially in individuals who smoke, as the combination of radon exposure and smoking significantly elevates the risk.