(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

We want to measure the specific activity (number of decays per second) of a radioactive source so that we can use it to calibrate the equipment of the gamma-ray experiment. We use an electronic counter and a timer to measure the number of decays in a given time interval. In round numbers we measure 1000 decays in 5 minutes of observation. For how long should we measure in order to obtain a specific activity with a precision of 1%? Explain.

2. Relevant equations

3. The attempt at a solution

I'm not sure where to begin. I thought about using the formula 1/sqrt(N), but wasn't sure if I could set that equal to the percent of precision (1%). I also hope I put this question in the right category. Thanks in advance!!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Finding Time Given Number Of Trials And Precision

**Physics Forums | Science Articles, Homework Help, Discussion**