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The mean lives of a radioactive substance are 1620 years and 405 years of `alpha`-emission and `beta`-emission respectively. Find out the time during which three-fourth of a sample will decay if it is decaying both by `alpha`-emission and `beta`-emission simultaneously. |
Answer» For succiessive `alpha, beta`-emission `K_("avg") = K_(alpha) + K_(beta) = (1)/(1620) + (1)/(405) = (5)/(1620) "years"^(-1)` Given at `t = t`, `N = 1//4 N_(0)` (since `3//4` part decays) `t = (2.303)/(K_("avg")) "log" (N_(0))/(N)` `= (2.303 xx 1620)/(5) "log" 4 = 449.24` years |
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