In 90 seconds, the mass of a radioactive element reduces to (frac{1}{16}) of its original value. Determine the half- life of the element.
-
A.
15.0s -
B.
18.0s -
C.
22.5s -
D.
30.0s -
E.
45.0s
Correct Answer: Option C
Explanation
(frac{1}{16} = (frac{1}{2})^n)
((frac{1}{2})^4 = (frac{1}{2})^n)
(n = 4)
90 secs = 4 half lives
1 half life = (frac{90}{4}) secs
= 22.5 secs