A student is determining the corrected count rate of a radioactive sample. The total count rate measured by the detector in the presence of the sample is RtotalR_{\text{total}}Rtotal, and the background count rate measured in the absence of the sample is RbackgroundR_{\text{background}}Rbackground.
Which of the following equations correctly expresses the corrected count rate of the sample, RsampleR_{\text{sample}}Rsample?
Rsample=Rtotal+RbackgroundR_{\text{sample}} = R_{\text{total}} + R_{\text{background}}Rsample=Rtotal+Rbackground
Rsample=Rtotal−RbackgroundR_{\text{sample}} = R_{\text{total}} - R_{\text{background}}Rsample=Rtotal−Rbackground
Rsample=Rbackground−RtotalR_{\text{sample}} = R_{\text{background}} - R_{\text{total}}Rsample=Rbackground−Rtotal
Rsample=Rtotal+Rbackground2R_{\text{sample}} = \frac{R_{\text{total}} + R_{\text{background}}}{2}Rsample=2Rtotal+Rbackground
484 exam-style questions on CIE IGCSE Physics 5.2 Radioactivity, covering 5.2.1 Background radiation and measuring count rate, 5.2.2a Alpha, beta and gamma emission, 5.2.2b Deflection and ionising effects of nuclear radiation, 5.2.3a Radioactive decay, 5.2.3b Effects of decay on the nucleus and decay equations, 5.2.4a Half-life, 5.2.4b Choosing isotopes for applications, and 5.2.5 Effects of ionising radiation and safety precautions. Each one has a worked solution and a mark scheme showing where the marks go.