If No is the original mass of the substance of half-life period T1/2=5 yr, then the amount of substance left after 15 yr is

Question

If No is the original mass of the substance of half-life period T1/2=5 yr, then the amount of substance left after 15 yr is (A) N0/8 (B) N0/16 (C) N0 /2 (D) N0 /4

Tardigrade Admin · Accepted Answer

T1 / 2=5 yr, t=15 yr ∴ Number of half-lives (n)=(t/T1 / 2)=(15/5)=3 The amount of substance left undecayed. N=N0((1/2))n =N0((1/2))3 =(N0/8)

Q. If No is the original mass of the substance of half-life period $T_{1/2} = 5 yr$ , then the amount of substance left after $15 yr$ is

$N_{0} /8$

$N_{0} /16$

$N_{0} /2$

$N_{0} /4$

$T_{1/2} = 5 yr, t = 15 yr$
$∴$ Number of half-lives
$(n) = \frac{t}{T _{1/2}} = \frac{15}{5} = 3$
The amount of substance left undecayed.
$N = N_{0} (\frac{1}{2})^{n}$
$= N_{0} (\frac{1}{2})^{3} = \frac{N _{0}}{8}$

Q. If No is the original mass of the substance of half-life period T1/2​=5yr, then the amount of substance left after 15yr is

N0​/8

N0​/16

N0​/2

N0​/4