A radioactive substance has a half life of 20 d... - JAMB Physics 2007 Question
A radioactive substance has a half life of 20 days. What fraction of the original radioactive nuclei will remain after 80 days?
A
\( \frac{1}{32} \)
B
\( \frac{1}{16} \)
C
\( \frac{1}{8} \)
D
\( \frac{1}{4} \)
correct option: b
80 days = 4 half lives (i.e 4 x 20dqs = 80dq)
But the fraction always left by any radioactive material after 4 half lives is
( \left ( \frac{1}{2} \right)^2 = \frac{1}{16} )
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