25. Rhodium-106 has a half-life of 30 mathrm(~s) . A sample of rhodium-106 has an activity of 3200 mathrm(Bq) The activity of this sample after 120 mathrm(~s) is: A 27 mathrm(~Bq) B 107 mathrm(~Bq) C 200 mathrm(~Bq) D 400 mathrm(~Bq) E 800 mathrm(~Bq) .

The question refers to nuclear decay and the concept of half-life. The half-life of a sample is the time it would take for half of the sample to decay. Examining the question and understanding this principle can help us perform the necessary calculations to find the answer. Rhodium-106 has a half-life of 30 seconds, and it is asked about the remaining activity after 120 seconds.The number of half-lives in 120 seconds is figured out by . The remaining fraction of the sample after 4 half-lives is calculated by . The activity, counted in Becquerels (referred to here with the abbreviation 'Bq'), is proportional to the amount of the sample: if the amount reduces to a 1/16 fraction, so will the activity.Multiply the original activity by the remaining fraction: .