A freshly prepared radioactive source of half life 2 hours 30 minutes emits radiation which is 64 times the permissible safe level. The minimum time, after which it would be possible to work safely with source, will be _________ hours.
Answer (integer)
15
Solution
<p>${T_{1/2}} = 150$ minutes</p>
<p>${A_0} = 64x$, where x is safe limit</p>
<p>$x = 64x \times {2^{ - {n \over {{T_{1/2}}}}}}$</p>
<p>$\Rightarrow {1 \over {64}} = {2^{ - {n \over {{T_{1/2}}}}}}$</p>
<p>or ${n \over {{T_{1/2}}}} = 6$</p>
<p>$\Rightarrow n = 6 \times 150$ minutes</p>
<p>= 15 hours</p>
About this question
Subject: Physics · Chapter: Atoms and Nuclei · Topic: Bohr's Model of Hydrogen Atom
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