The half-life for radioactive decay of potassium into argon is 1.3 billion years.A rock is found with 10 atoms of potassium and 90 of argon.What can we say about the age of the rock?
A)It formed less than a billion years ago
B)It formed about 1.3 billion years ago
C)It is much older than 1.3 billion years
D)It is much older than 20 billion years

Question

Quizplus · Accepted Answer

Given the half-life of potassium into argon is 1.3 billion years, and the current ratio of potassium to argon is 1:9, this indicates that multiple half-lives have passed, making the rock significantly older than 1.3 billion years. Each half-life would reduce the amount of potassium by half while increasing argon correspondingly.

The Half-Life for Radioactive Decay of Potassium into Argon Is