A radioactive substance decays to ${\left( {{1 \over {16}}} \right)^{th}}$ of its initial activity in 80 days. The half life of the radioactive substance expressed in days is ____________.
Answer (integer)
20
Solution
$${N_0}\buildrel {{{{t_1}} \over 2}} \over
\longrightarrow {{{N_0}} \over 2}\buildrel {{{{t_1}} \over 2}} \over
\longrightarrow {{{N_0}} \over 4}\buildrel {{{{t_1}} \over 2}} \over
\longrightarrow {{{N_0}} \over 8}\buildrel {{{{t_1}} \over 2}} \over
\longrightarrow {{{N_0}} \over {16}}$$<br><br>$4 \times {t_{1/2}} = 80$<br><br>${t_{1/2}} = 20$ days
About this question
Subject: Physics · Chapter: Atoms and Nuclei · Topic: Radioactivity
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