1. Radioactive Decay. People often wonder how scientists are able to determine things such as the ages of rocks or the Earth. This is most frequently done by taking advantage of a neat process in nature called radioactive decay. When a radioactive substance breaks down it does so in a very systematic manner, and we can measure the rate of these break downs (or decays) to determine how old an object is— basically the amount of radioactive stuff left over can tell us how old the substance is. The rate of break down is often referred to as the half-life. For example, Beryllium 10 (10Be) breaks down into Boron 10 (10B) with a half-life of 1.36 million years. This means that if you start out with a solid block of 10Be in 1.36 million years, half of the block will still be 10Be and the other half will be 10B. After each increment of the half-life, 1/2 of remaining radioactive material (10Be) will become the decay product, in this case.
a How much of a block that was originally all 10Bewi I I still be 10Be and how much will be 10B after a total of 4.08 million years?
b. If you come across a block that is 1/32 1°Beand 31/32 1013, can you unambiguously determine its age? If so, what is the agO??f not, why not?
Now what are you supposed to do if you come across a block that has 72% 1°Be and 28% 10B, or a block that is 0.23 million years old – how do you deal with these quantities to determine ages or amounts of material?