Radioactivity in the air The average activity of air inside homes in the United States is about 1.5 pCi per liter. What is the average activity of a liter of air, in Bq? In decays per hour?

Question

Radioactivity in the air

The average activity of air inside homes in the United States is about 1.5 pCi per liter. What is the average activity of a liter of air, in Bq? In decays per hour?

Accepted Answer

SET UP We use the average value just cited, 1.5 pCi/L, along with the conversion factor [latex]\mathrm{1 Ci = 3.7 imes 10^{10} Bq.}[/latex]

SOLVE [latex]\mathrm{1.5 pCi/L = (1.5 imes 10^{-12} Ci/L)\left(\frac{3.70 imes 10^{10} Bq}{1 Ci} ight) } [/latex]

= 0.056 Bq.

Since 1 Bq = 1 decay/s, the number of decays in 1 hour is

(0.056 decays/s)(3600 s/h) = 200 decays/h.

REFLECT A level of activity of air of 1.5 pCi/L represents, on average, the decay of one Rn nucleus every 18 s in each liter of air. If the basement of a medium-size house has a volume of [latex]10^6 L[/latex], the total activity of the air in this basement is about [latex]\mathrm{1.5 imes 10^{-6} Ci, or about 5 imes 10^4}[/latex] disintegrations per second.

Practice Problem: If your lungs contain an average of 5.0 L of air, how many decays occur each minute? Answer: 17.

Question 30.6: Radioactivity in the air The average activity of air inside ...

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