Radioactive half-life is a term used to describe the time it takes for half of the radioactive atoms in a substance to decay or break down. Radioactive atoms are unstable and naturally undergo a process called radioactive decay, where they transform into different atoms or release particles and energy.

Imagine you have a jar filled with a certain number of radioactive atoms. After a specific amount of time, let’s say one hour, half of the atoms in the jar will have decayed, meaning they have transformed or released particles. The remaining half will still be radioactive. After another hour, half of the remaining radioactive atoms will decay, leaving only a quarter of the original amount. This process continues over time.

The half-life is the time it takes for half of the radioactive atoms to decay. Different radioactive substances have different half-lives. For example, the half-life of a particular radioactive element may be one hour, while for another element, it could be thousands or even millions of years. Scientists use the concept of half-life to measure the stability and decay rate of radioactive substances.

Understanding half-life is important because it helps scientists determine how long a radioactive substance will remain active or dangerous. It also helps in various fields such as medicine, archaeology, and geology, where radioactive elements are used to study and analyse different materials and processes.

**Instructions:**

- Read each question carefully.
- Solve the problems and write your answers in the spaces provided.
- Show all your calculations and provide units where necessary.
- If you need any assistance, feel free to ask.

**Question 1:**

The half-life of a radioactive substance is 10 years. If you start with 200 grams of the substance, how much will be left after 30 years?

**Question 2:**

A sample of radioactive material has a half-life of 5 days. If the initial mass is 100 grams, how much will remain after 15 days?

**Question 3:**

The half-life of a certain radioactive element is 2 hours. If you start with 80 milligrams of the element, how much will be left after 6 hours?

**Question 4:**

A radioactive substance has a half-life of 1 minute. If you start with 500 micrograms of the substance, how much will remain after 5 minutes?

**Question 5:**

The half-life of a radioactive isotope is 20 years. If you start with 1000 grams of the isotope, how much will remain after 60 years?

**Question 6:**

A sample of radioactive material has a half-life of 8 hours. If the initial mass is 250 grams, how much will remain after 24 hours?

**Question 7:**

The half-life of a certain radioactive element is 1 day. If you start with 1200 milligrams of the element, how much will be left after 4 days?

**Question 8:**

A radioactive substance has a half-life of 2 seconds. If you start with 10 milligrams of the substance, how much will remain after 8 seconds?

**Question 9:**

The half-life of a radioactive isotope is 30 minutes. If you start with 500 grams of the isotope, how much will remain after 90 minutes?

**Question 10:**

A sample of radioactive material has a half-life of 6 days. If the initial mass is 400 grams, how much will remain after 18 days?

**Answer Key:**

- 50 grams
- 6.25 grams
- 10 milligrams
- 3.125 micrograms
- 62.5 grams
- 15.625 grams
- 75 milligrams
- 0.3125 milligrams
- 62.5 grams
- 25 grams

Remember to check your answers and make sure you understand how to calculate radioactive decay using half-life.