Half-Life Formula

Half-Life Formula

It is the time requires to decay in half. Half-life is the time required for the amount of something to fall to half its initial value. The mathematical representation of Half life is given by,

(Half life time) = (Napierian logarithm of 2)/(disintegration constant)

The equation is:

t1/2 = ln(2)/λ


λ : disintegration constant of the system

t1/2: Half life time

Half-life Formula Questions:

1) What is the half life of a radioactive substance whose disintegration constant is 0.005 years(-1)?


Substituting the data in the half-life formula

t1/2 = ln(2)/(0.005 years(1))

t1/2 = ln(2)*200 years

t1/2 = 138.62 years

2) What is the disintegration constant of a process whose half life time is 10 minutes?


From the half-life formula we find the disintegration constant

λ = ln(2)/t1/2

λ = ln(2)/(600 s)

λ = 0.00115 s(-1)

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