A radioactive material decays by simulataneous emission of two particle from the with respective half - lives `1620` and `810` year . The time , in year , after which one - fourth of the material remains is

Options

A. 1080
B. 2430
C. 3240
D. 4860

Answer

A

Explanation

(a) `lambda = lambda_(1) + lambda_(2)`
`(1)/(T) = (1)/(T_(1)) + (1)/(T_(2))`
`:. T = (T_(1) xx T_(2))/(T_(1) + T_(2)) = (810 xx 1620)/(810 xx 1620) = 540 yr`
Hence, `(1)/(4)` th material reamin after `1080 yr`.