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13.Nuclei
medium
A radioactive element has half life period $800$ years. After $6400$ years what amount will remain?
A
$\frac{1}{4}$
B
$\frac{1}{16}$
C
$\frac{1}{8}$
D
$\frac{1}{256}$
(AIPMT-1989)
Solution
Fraction $=\frac{\mathrm{N}}{\mathrm{N}_{0}}=\left(\frac{1}{2}\right)^{\frac{6400}{800}}=\left(\frac{1}{2}\right)^{8}=\frac{1}{256}$
Standard 12
Physics