If N 0 is the initial mass of a substance with half-life t 1 2 = 5 y e a r s , then the amount of substance left after 15 y e a r s is

N 0 is the initial amount of substance and N is the amount left after decay. Thus, N = N 0 1 2 n n = no. of half lives = t t 1 / 2 = 1 5 5 = 3 Therefore, N = N 0 1 2 3 = N 0 8

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PhysicsModern PhysicsRadioactivityEasy2 minPYQ_2020

PhysicsEasysingle choice

If $N_{0}$ is the initial mass of a substance with half-life $t_{\frac{1}{2}} = 5 y e a r s$ , then the amount of substance left after $15 y e a r s$ is

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Answer:

Solution:

$N_{0}$ is the initial amount of substance and $N$ is the amount left after decay.

Thus, $N = N_{0} {(\frac{1}{2})}^{n}$

n = no. of half lives $= \frac{t}{t_{1 / 2}} = \frac{15}{5} = 3$

Therefore, $N = N_{0} {(\frac{1}{2})}^{3} = \frac{N_{0}}{8}$

Stream:NTA_ABHYAS_NEETSubject:PhysicsTopic:Modern PhysicsSubtopic:Radioactivity

⏱ 2mℹ️ Source: PYQ_2020

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