An unknown radioactive sample is observed to decrease in activity by a factor of two in a one hour period. What is its half-life?

The half-life is

Explanation:

Using the decay equation we have:

Where:

We know the activity decrease by a factor of two in a one hour period (t = 1 h), it means that

Taking the natural logarithm on each side we have:

Now, the relationship between the decay constant λ and the half-life t(1/2) is:

I hope it helps you!

trig 15.3 cos

conservation of mass

mass before something happens = mass afterwards