Question

A radio isotope ‘X’ with a half life 1.4 × 10⁹ years decays to
‘Y’ which is stable. A sample of the rock from a cave was
found to contain ‘X’ and ‘Y’ in the ratio 1 : 7. The age of the
rock is : [2014]
(a) 1.96 × 10⁹ years (b) 3.92 × 10⁹ years
(c) 4.20 × 10⁹ years (d) 8.40 × 10⁹ years

Answer 1

Answer:

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 1:7 in a sample of a given rock. The age of the rock is estimated to be.