Physics: Atomic Theroy

Question

Suppose a wood fossil was found to be one eighth as C-14 radioactive as the same wood today. How old is it? (answer to the nearest 10 years, i.e. 5010 years, not 5011)

Answer 1

This is a type of question that gets asked in chemistry(!) classes when the topic is nuclear chemistry. Anyway, the definition of half-life is the time it takes for 1/2 of the amount present at the start of the time period to decay. These are a geometric series - each passing half-life cuts the amount present by a factor of 1/2.

 

Since 1/8 = (1/2)³, it means that 3 half-lives have passed. The half-life of C-14 is 5730 years. The last bit is left as an exercise for the student.

 

Jim Scripko