The half life of the radioactive substance is 10.22 years.
<h3>What is Half Life ?</h3>Half Life is the amount of time needed by the radioactive substance to reduce to its half concentration (as compared to the initial concentration).
It is given that
y = ae⁻ᵇˣ
here a is the initial amount , y is the amount remaining after x years
a = 90mg at x =0
Value of y = 12.6 mg at x = 29 years
On substitution of value
12.6 = 90 e⁻²⁹ᵇ
0.14 = e⁻²⁹ᵇ
b = 0.0678
The equation is
Half life is when the concentration is reduced to half
On 1st half life , the concentration = 90/2 = 45 mg
x = 10.22 years
Therefore the half life of the radioactive substance is 10.22 years.
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