Indoor air pollution. Uranium is naturally present in rock and soil. At one step in its series of radioactive decays, 238U produces the chemically inert gas radon-222, with a half-life of 3.82 days. The radon seeps out of the ground to mix into the atmosphere, typically making open air radioactive with activity 0.3 pCi/L. In homes, 222Rn can be a serious pollutant, accumulating to reach much higher activities in enclosed spaces. If the radon activity exceeds 4 pCi/L, the Environmental Protection Agency suggests taking action to reduce it, such as by reducing infiltration of air from the ground.
(a) Suppose that the activity is actually 5.7 pCi/L. Convert this to units of becquerel per cubic meter.
(b) How many 222Rn atoms are in one cubic meter of air displaying this activity?
(c) What fraction of the mass of the air does the radon constitute?