A measurement is recorded every 10 minutes for the number of emissions per second from a radioactive source. The table lists the measurements. Time / min: 0, 10, 20, 30, 40, 50, 60 Number of emissions per second: 800, 560, 400, 280, 200, 140, 100 What is the half-life of the source?
- A10 min
- B20 min
- C40 min
- D60 min