A science communicator explains exponential decay using a radioactive isotope with a half-life of 8 years. If a sample initially weighs 640 grams, how much remains after 24 years?

Tue, 05 May 2026 22:38:14 +0000

**A science communicator explains exponential decay using a radioactive isotope with a half-life of 8 years. If a sample initially weighs 640 grams, how much remains after 24 years?** When people ask what happens to a radioactive substance over time, understanding half-life offers a clear, mathematical framework—one increasingly relevant in fields from environmental science to nuclear waste management. Here’s how it applies: A radioactive isotope with a half-life of 8 years decays by half every 8 years. After 24 years—three half-lives—the original sample will have undergone significant transformation, and its remaining mass reveals the powerful predictability of exponential decay. Using the half-life model, the amount remaining after 24 years is calculated by determining how many half-lives fit into 24 years. Since 24 divided by 8 equals 3, the sample undergoes decay over three full half-lives. Starting with 640 grams: After the first 8 years: 640 ÷ 2 = 320 grams
After 16 years: 320 ÷ 2 = 160 grams
After 24 years: 160 ÷ 2 = 80 grams