`1.0 g` of a radioactive isotope left `125 mg` after 24 hr. The half-life period of the isotope is
a. 8 hr b. 24 hr c. 6 hr d. 4 hr

Options

A. 8 hours
B. 24 hours
C. 6 hours
D. 4 hours

Answer

A

Explanation

`N=[(1)/(2)]^(n) xx N_(0)`
125 mg `=[(1)/(2)]^(n)xx1000` mg
`((1)/(2))^(n)=(125)/(1000)=(1)/(8)`
`((1)/(2))^(n)=((1)/(2))^(3)`
So no. of half lives=3
Total time =24 hours
Half life time `=(24)/(3)=8` hours