Aparent isotope has a half life of 1 million years. if a rock contained 20 mg of the parent isotope when it formed, how much parent isotope would be left after 2 million years?

mg parent isotope would be left after 2 million years

Explanation:

It is given that half life of parent isotope is equal to one million years.

Half life period indicates the number of years required by an isotope to reduce its quantity by half.

Amount of parent isotope left after first half life period i,e after million years

mg

Amount of parent isotope left after second half life period i,e after million years

mg