Tests on human subjects along the East Coast of the United States in 1965 and 1966, following the era of atomic bomb testing, revealed quantities of about 1.11 pCi of plutonium radioactivity (alpha radiation) in a test subject. A 75-kg person is exposed to this radiation for 1.00 year (365 days). If each alpha particle deposits 8.00×10?13 J what is the number of rads absorbed by the person? Express your answer in rads using two significant figures. Solution activity = 1.11 pCi = 1.11 x 10^ -12 ci = 1.11 x 10^ -12 x 3.7 x 10^ 10 dps = 0.04107 dps ( where dps = distingetrations per second) 1 year has 3.154 x 10^ 7 seconds per year disitintegrations = 0.04107 disintegrations / s x 3.154 x 10^ 7 s = 1295348 Thus per year 1295348 alphs particles produced Energy produced = 1295348 x 8 x 10^ -13 = 1.036 x 10^ -6 J dose = energy absorbed / mass of body = 1.036 x 10^ -6 J / ( 75 kg) = 1.38 x10^ -8 J/kg = 1.38 x 10^ -6 x ( 0.01 J/kg) = 1.4 x 10^ -6 rad .

1. Tests on human subjects along the East Coast of the United States in 1965 and 1966, following
the era of atomic bomb testing, revealed quantities of about 1.11 pCi of plutonium radioactivity
(alpha radiation) in a test subject.
A 75-kg person is exposed to this radiation for 1.00 year (365 days). If each alpha particle
deposits 8.00×10?13 J what is the number of rads absorbed by the person?
Express your answer in rads using two significant figures.
Solution
activity = 1.11 pCi = 1.11 x 10^ -12 ci = 1.11 x 10^ -12 x 3.7 x 10^ 10 dps = 0.04107 dps
( where dps = distingetrations per second)
1 year has 3.154 x 10^ 7 seconds
per year disitintegrations = 0.04107 disintegrations / s x 3.154 x 10^ 7 s
= 1295348
Thus per year 1295348 alphs particles produced
Energy produced = 1295348 x 8 x 10^ -13 = 1.036 x 10^ -6 J
dose = energy absorbed / mass of body
= 1.036 x 10^ -6 J / ( 75 kg) = 1.38 x10^ -8 J/kg
= 1.38 x 10^ -6 x ( 0.01 J/kg)
= 1.4 x 10^ -6 rad