Question

A radioactive sample at any instant has its disintegration rate 5000 disintegration per minute. After 5 minutes, the rate is 1250 disintegrations per minute. Then, the decay constant (per minute) is-

• A. 0.8 ln 2
• B. 0.4 ln 2
• C. 0.2 ln 2
• D. 0.1 ln 2

Answer 1

Answer: (B)

0.4 ln 2

Answer 2

A.P = $\frac { 1 } { 4 }$ = (n = 2), T_1/2 = $\frac { \mathrm { t } } { \mathrm { n } }$=$\frac { 5 } { 2 }$= 2.5 min

l = = = 0.4 ln2