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:

  1. (d) No. of half lives, $n=\frac{t}{T}=\frac{6400}{800}=8$

$\frac{N}{N_0}=(\frac{1}{2})^{8}=\frac{1}{256}$