The strength of a radioactive substance decreases 50% in a 30-day period. How long will it take for the radioactivity to decrease to 1% of its initial value?
The standard formula for radioactive decay, as you know, is , where is the initial amount, is the time elapsed, and is the half-life (with and being measured in consistent units). So for the material to reach 1% of its initial value, . Therefore, simply isolate t in the following equation: