GENERAL KNOWLEDGE

Detailed explanation-1: -Mean life: It is the sum of the life span of a specific number of nuclei divided by the number of nuclei. Let dN be the number of nuclei disintegrate in the time interval dt. For example, the mean life of a 14C nucleus with T1/2 = 5730 is 8267 years.

Detailed explanation-2: -mean life, in radioactivity, average lifetime of all the nuclei of a particular unstable atomic species. This time interval may be thought of as the sum of the lifetimes of all the individual unstable nuclei in a sample, divided by the total number of unstable nuclei present.

Detailed explanation-3: -To calculate the average life, multiply the date of each payment (expressed as a fraction of years or months) by the percentage of total principal that has been paid by that date, add the results, and divide by the total issue size.

Detailed explanation-4: -Average life. The average life of a radioactive substance is the ratio of sum of lives of all the atoms to the total number of atoms. ∴dN=−N0e−tdt. It means that dN atoms disintegrate between time t and t + dt i.e. they have survived for time t.

Detailed explanation-5: -Solution. The mean life time of the nucleus is the ratio of sum or integration of life times of all nuclei to the total number nuclei present initially. The expression for a mean life time, = . Concept: Radioactivity.