Question

Half-life period of a radioactive element is 100 yr. How long will it take for its 93.75% decay ?

• A. 400 yrs
• B. 300 yrs
• C. 200 yrs
• D. 193 yrs

Answer 1

The correct option is A 400 yrs

Given : Half-life period of a radioactive element is 100 yr. How long will it take for its 93.75% decay ?

Solution :

Since it is decayed by 93.75 % so left is 6,25%

That is $\frac{1}{16}$ of total element

$\frac{1}{2^n}$= $\frac{1}{16}$ where n is number of half life.

n=4

To decay 93.75% time needed is $4\times half-life$ = $4\times 100$ = 400 yr

The Correct Opt = A