The half-life of a radioactive isotope 'X' is 50 years. It decays to another element 'Y' which is stable. The two elements 'X' and 'Y' were found to be in the ratio of 1:15 in a sample of a given rock. The age of the rock was estimated to be
150 years
200 years
250 years
100 years
As we learnt in
Number of nuclei in terms of half life -
- wherein
Very useful to determine number of nuclei in terms of half life
At any time Ratio of X and Y is 1:15
if number of nuclei of X is N
then number of nuclei of Y is 15 N
Total number of nuclei initially and finally must be equal
Option 1)
150 years
Incorrect
Option 2)
200 years
Correct
Option 3)
250 years
Incorrect
Option 4)
100 years
Incorrect