Saved Bookmarks
| 1. |
Define ‘disintegration constant’ and ‘mean life’ of a radioactive substance. Give the unit of each. |
|
Answer» Solution :Disintegration or decay constant : ACCORDING to LAW of radioactive decay the instantaneous rate of disintegration `(-(dN)/(dt))` of a radioactive element is directly proportional to the actual number of nuclides of that element present at that instant i.e., `-(dN)/(dt)=lambdaN`, where `lambda` is the disintegration constant. Hence, disintegration constant of a radioactive substance is defined as the ratio of its instantaneous rate of disintegration to the number of nuclides present at that TIME. Its SI unit is `s^(-1)`. MEAN life : Mean life of a radioactive substance is the time at which the rate of disintegration (ie., ACTIVITY) as well as the number of nuclides left undecayed have been reduced to `e^(-1)(or 1/eth)` of their initial values. SI unit of mean life is second. Disintegration constant is reciprocal of mean life i.e, `lambda = 1/tau`, where `tau` is the mean life. |
|