A building has become accidentally contaminated with radioactivity. The longest-lived material in the building is strontium-90. (Th 90 Sr is 89.9077 u.) If the building initially contained 7.7 kg of this substance and the safe level is less than 38 atomic mass of 10.3 counts/min, how long will the building be unsafe?

A 75 kg patient swallows a 33 μCi beta emitter whose half-life is 5.0 days and whose RBE is 1.6. The beta particles are emitted with an average energy of 0.35 MeV, 90% of which is absorbed by the body. You are a health care worker needing to find the patient's dose equivalent after one week. These series of steps will help you find that dose equivalent. In all questions, assume the radioactive nuclei are distributed throughout the patient's body and are not being excreted. Part A How many radioactive nuclei did the patient swallow? Express your answer using three significant figures. ▸ View Available Hint(s) No= ΜΕ ΑΣΦ Submit ?

A sample of radioactive material has a half-life of 12 hours. If the initial sample contained 6.2x10¹3 radioactive nuclides estimate the number of radioactive nuclides present in the sample after 5 hours.

In 1992, Swiss police arrested two men who were attempting to smuggle osmium out of Eastern Europe for a clandestine sale. However, by error, the smugglers had picked up 137Cs. Reportedly, each smuggler was carrying a 1.0 g sample of 137Cs in a pocket! In (a) bequerels and (b) curies, what was the activity of each sample? The isotope 137Cs has a half-life of 30.2 y. (The activities of radioisotopes commonly used in hospitals range up to a few millicuries.)

Please both