A sample of volcanic rock contains of potassium-40 and of radiogenic argon-40…

PHYSICS · Multi-part · A Level · Physics · Nuclear physics · Nuclear physics

Problem

A sample of volcanic rock contains

2.4\times10^{-4}\,\text{mol}

of potassium-40 and

1.8\times10^{-4}\,\text{mol}

of radiogenic argon-40 produced by its decay. Assume that no argon-40 was present when the lava solidified and that every decay of

^{40}

K in the mode considered produces one

^{40}

Ar atom. The half-life of

^{40}

K is

1.28\times10^{9}\,\text{years}

. (a) Write the mathematical expression you will use to relate the given quantities to the age of the rock. (b) Calculate the age of the volcanic rock to two significant figures.

Related theory

Radioactivity
Nuclear physics
Radioactive decay

Browse the problem library