Physics – 5.2.1 Detection of radioactivity | e-Consult

To calculate the background radiation count rate, we subtract the unshielded count rate from the shielded count rate. This is because the shielded count rate represents the radiation from the source *plus* the background radiation. Therefore, subtracting the unshielded count rate isolates the background radiation.

Background Radiation Count Rate = Shielded Count Rate - Unshielded Count Rate

Background Radiation Count Rate = 10 counts/minute - 40 counts/minute = -30 counts/minute

There appears to be an error in the provided data, as the background radiation count rate cannot be negative. The unshielded count rate should be *lower* than the shielded count rate. Assuming the data is correct, the calculation would yield -30 counts/minute. However, in a real experiment, the unshielded count rate should be significantly higher than the shielded count rate. A more realistic scenario would be, for example, Shielded = 10 CPM and Unshielded = 50 CPM, resulting in a background rate of 40 CPM.