The initial mass of a radioactive element is `40g`. How many grams of it would be left after 24 years if its half`-` life period I s of 8 years ?

Options

A. 2
B. 5
C. 10
D. 20

Answer

B

Explanation

`T=nxxt_(1//2)`
`:. n=(T)/(t_(1//2))=(24)/(8)=3`
`N=((1)/(2))^(3)N_(0)`
`:. N=((1)/(2))^(3)xx40=(40)/(8)=5`