Question

After two half-lives, how much of the original material has decayed? 25 percent 50 percent 75 percent 100 percent

Answer 1

The original material has decayed 75%

Further explanation

Given

two half-life

Required

The decayed sample

Solution

General formulas used in decay:  

$\large{\boxed{\bold{N_t=N_0(\dfrac{1}{2})^{t/t\frac{1}{2} }}}$

t = duration of decay  

t 1/2 = half-life  

N₀ = the number of initial radioactive atoms  

Nt = the number of radioactive atoms left after decaying during T time

t = 2 x t 1/2

Input the value :

$\tt \dfrac{Nt}{No}=\dfrac{1}{2}^2=\dfrac{1}{4}=25\%$  

The amount of Nt = 25% No