From a newly formed radioactive substance (Half-life 2 hours), the intensity of radiation is 64 times the permissible safe level. The minimum time after which work can be done safely from this source is

6 hours

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12 hours

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24 hours

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128 hours

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Solution

The correct option is B 12 hours
By using $A = A_{0} {(\frac{1}{2})}^{n} \Rightarrow \frac{A}{A_{0}} = \frac{1}{64} = {(\frac{1}{2})}^{6} = {(\frac{1}{2})}^{n} \Rightarrow n = 6$
$\Rightarrow \frac{t}{T_{\frac{1}{2}}} = 6 \Rightarrow t = 6 \times 2 = 12 h o u r s$ .

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From a newly formed radioactive substance (Half-life 2 hours), the intensity of radiation is 64 times the permissible safe level. The minimum time after which work can be done safely from this source is

The correct option is B 12 hoursBy using A=A0(12)n⇒AA0=164=(12)6=(12)n⇒n=6 ⇒ tT12=6⇒t=6×2=12 hours.

The correct option is B 12 hours
By using $A = A_{0} {(\frac{1}{2})}^{n} \Rightarrow \frac{A}{A_{0}} = \frac{1}{64} = {(\frac{1}{2})}^{6} = {(\frac{1}{2})}^{n} \Rightarrow n = 6$
$\Rightarrow \frac{t}{T_{\frac{1}{2}}} = 6 \Rightarrow t = 6 \times 2 = 12 h o u r s$ .