Final answer:
The question involves calculating the rem dose to a tumor during radiation therapy with a Co-60 source, considering the gamma ray energy and proportions of rays absorbed. The calculation requires energy conversion and understanding of radiation dosimetry and safety in medical treatments.
Step-by-step explanation:
The question relates to the calculation of radiation dose received by a tumor during a medical procedure using a radioactive source. Specifically, the question asks to calculate the dose in rem delivered to a tumor when a cancer patient is exposed to gamma rays from a cobalt-60 (Co-60) source. In the scenario described, only 1.00% of the gamma rays are directed at the patient, and of those, 20.0% are absorbed by the tumor. The average gamma ray energy per decay is given as 1.25 MeV.
To calculate the dose in rem, one must first convert the energy absorbed from MeV to joules, then divide by the mass of the tumor, and finally convert the absorbed dose from gray to rem using the appropriate conversion factor. Comparing the calculated dose with standard therapeutic doses will determine its consistency with common medical practices. Additionally, understanding the principle that only a small fraction of beta particles from decay interact with the patient is important for evaluating the effectiveness and safety of the treatment.