Radioactive isotopes break down over time and the amount pre

Radioactive isotopes break down over time and the amount present in a substance decays exponentially. The half-life of a radioactive isotope is defined to be how much time it takes for the amount present m a substance to decrease by half. In the early 1960s, radioactive strontium-90 was released during atmospheric testing of nuclear weapons and got into the bones of people alive at the time. If the half-life of strontium-90 is 31 years, what fraction of the strontium-90 absorbed in 1962 remained in people\'s bones in 2000? fraction = (Enter your answer as a decimal or fraction.)

Solution

decay constant = 0.693/half life

= 0.693/31 = 0.022

The decay equation : N(t) = Noe^(-kt)

N(t) = Noe^(-0.022t)

t = 2000 - 1962 = 38 yrs

N(t) = Noe^(-0.022*38) = No*0.43

Fraction of Strontium -90 absorbed = (1- 0.43) = 0.57