Question

10g of a radioactive isotope is reduced to 1.25 g in 12 years. Therefore, half-life period of the
isotope is


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Answer 1

According to the formula,

Initial mass / 2ˣ = final mass

(where x = number of half lives)

10 / 2ˣ = 1.25

2ˣ = 10 / 1.25

2ˣ = 8

2ˣ = 2³

x = 3

Thus in 12 years, the radioactive isotope passes through 3 half lives.

so, half-life time = 12/3 = 4 years

Hope it helps!!