The half life of a radioactive isotope ‘X’ is 20 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 : 7 in a sample of a the given rock. The age of the rock is estimated to be
Options
(a) 60 years
(b) 80 years
(c) 100 years
(d) 40 years
Correct Answer:
60 years
Explanation:
The value of x is 1/8
= x₀/8 = x₀/2³ ⇒ t = 3t = 3 x 20 = 60 yrs
Hence the estimated age of rock is 60 yrs.