Strontium90 is one of the products of the fission of uranium

Strontium-90 is one of the products of the fission of uranium-235. This strontium isotope is radioactive, with a half-life of 28.1 yr. Calculate how long it will take for 0.500 g of the isotope to be reduced to 0.150 g by decay.

The carbon-14 decay rate of a sample obtained from a young tree is 0.332 disintegration per second per gram of the sample. Another wood sample prepared from an object recovered at an archaeological excavation gives a decay rate of 0.129 disintegration per second per gram of the sample. What is the age of the object?

Solution

Basically, you can only calculate the time taken for half the strontium to decay, not anywhere in between because radioactive decay is random. so to get to 0.25g, it would take 56.2 years. an estimated time for it to be reduced to 0.2g would be about 60 years. the formula to calculate it is half life x 2^n, where n is the number of half life\'s the substance has gone through.