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PhysicsModern PhysicsRadioactivityMedium2 minQB

PhysicsMediumsingle choice

A radioactive material has a mean life 1620 years and 520 years for $α$ and $β$ emissions respectively. The material decays by simultaneous $α$ and $β$ emissions. What is the time in which $\frac{1}{4}$ of material is intact?

Options:

Answer:

Solution:

$λ = \frac{1}{1620} + \frac{1}{520} = 2.54 \times 1 0^{- 3} y^{- 1}$

$T_{1/2} = \frac{ln 2}{λ} \approx 273 y$

1/4 intact means two half-lives:

$t = 2 \times 273 \approx 545 years$

Hence option (C).

Stream:JEESubject:PhysicsTopic:Modern PhysicsSubtopic:Radioactivity

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