If N0 is the original mass of the substance of half-life period

• Matter & Atoms

If N₀ is the original mass of the substance of half-life period t_1/2 = 5 years, then the amount of substance left after 15 years is

1. N₀/16
2. N₀/8
3. N₀/4
4. N₀/2

Answer

Amount left after decay is given by N

N = N₀(1/2)ⁿ

n = number of half lives = t/t_1/2= 15/5 = 3

Therefore,

Amount left = N = N₀(1/2)³

= N₀/8

The correct option is B.