Nuclei - Result Question 95
98. A radioactive element has half life period 800 years. After 6400 years what amount will remain?
[1989]
(a) $\frac{1}{2}$
(b) $\frac{1}{16}$
(c) $\frac{1}{8}$
(d) $\frac{1}{256}$
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Answer:
Correct Answer: 98. (d)
Solution:
- (d) No. of half lives, $n=\frac{t}{T}=\frac{6400}{800}=8$
$\frac{N}{N_0}=(\frac{1}{2})^{8}=\frac{1}{256}$
