Respuesta :
The half-life gives the time after which a give unstable substance decays
to half the initial quantity.
- The pair of percentages that describes the sample after two half-lives is; 25% unchanged and 75% stable.
Reasons:
The mass of the sample of the radioactive isotope, m = 60-g
The number of half lives that passes = 2 half lives
Required:
The pair of percentages that describes the sample.
Solution:
The half-life is the time half of an unstable radioactive substance decays into a stable substance.
Therefore, after one half life, the pair of percentages we have are;
50% unchanged and 50% stable
After the second half life, the 50% of the sample decays further by half to give; 25% stable substance and 25% unchanged substance
Therefore, after two half-lives, we get;
(50% + 25%) stable substance and 25% unchanged sample
75% stable substance and 25% unchanged
The correct option is; 25% unchanged and 75% stable.
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