The biological activity of some organs can be investigated using radioactive isotopes. For example,… Show more The biological activity of some organs can be investigated using radioactive isotopes. For example, iodine is important in the action of the thyroid. A subject is injected with a small amount of radioactive 131I and after a few days the following measurements are made with a Geiger counter: 1. The counter is placed in contact with the abdomen and 2750 counts per second are observed. Six days later the counter records 600 counts per second. 2. With the counter over the thyroid, 5500 counts per second are observed and 6 days later 3290 counts per second are observed. a. If the physical half-life of 131I is 194 hr, what is the biological half-life of iodine in the bulk of the human body? • Show less