Question

The half life of radioactive Radon is `3.8 days` . The time at the end of which `(1)/(20) th` of the radon sample will remain undecayed is `(given log e = 0.4343 ) `
A. `3.8` days
B. `1.65` day
C. `33` day
D. `76` day

Answer 1

Correct Answer - B
`M = M_(0)e^(-lambdat) rArr (M_(0))/(20) = M_(0)e^(-lambdat) rArr ln (1/20) = -lambdat`
`rArr ((ln(20))/(ln2)) T_(1//2) = t rArr ((ln(2) + ln(10))/(ln2))T_(1//2) = t`
`rArr t = 16.42` days