Half-life of a radioactive substance is 40 years. How long will it take to reduce to one fourth of i

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13.Nuclei

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The half-life of a radioactive substance is $40$ years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant

A

$40\, year,\, 0.9173/year$

B

$90\ year, 9.017/year$

C

$80\, year, 0.0173 \,year$

D

None of these

Solution

(c) To reduce one fourth it takes time $t = 2\left( {{T_{1/2}}} \right) = 2 × 40$

$= 80 \,years.$

Decay constant $\lambda = \frac{{0.693}}{{{T_{1/2}}}} = \frac{{0.693}}{{40}} = 0.0173\,years$

Standard 12

Physics

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