By Suman Patra
The half-life of a radioisotope is the time required for half the atoms in a given sample to undergo radioactive, or nuclear, decay.
Initially, at time t = 0, the sample is 100%.
After 50 days, only half the original amount of element will remain:
½ x 100% = 50%
After another 50 days, only half of this amount of will remain:
½ x 50% = 25%
After another 50 days, only half of this amount of strontium will remain:
½ x 25% = 12.5%
This can be represented in the form of a table:
|Number of Half-lives||Time (Days)||% of Radioactive element remaining||% of Radioactive element decayed|
Hence, we can see that there are 3 half lives required for the element to become 12.5% of the original amount.
In case you need to calculate the percentage remaining after some other number of days or years or hours, you can use the formula;
Nt = No X (0.5)Number of half-lives
Nt = Amount of radioisotope remaining
No = Original amount of radioisotope
Number of half-lives = Time ÷ Half-life
No = 100%
(Time is the number of days or years or hours given).