Sagot :
[tex]t_{\frac{1}{2}}=5730\\
N_0=120\ g\\
t=2t_{\frac{1}{2}}=2\cdot5730=11460\\
N(t)=?\\\\
N(t)=N_0\left(\frac{1}{2}\right)^{\frac{t}{t_{\frac{1}{2}}}}\\
N(11460)=120\cdot\left(\frac{1}{2}\right)^{\frac{11460}{5730}}\\
N(11460)=120\cdot\left(\frac{1}{2}\right)^2\\
N(11460)=120\cdot\frac{1}{4}\\
N(11460)=30\ g[/tex]
After one half-life . . . 1/2 of the total parent material
After another half-life . . . 1/2 of the half remains = 1/4 of the total original parent
If the original parent is 120 grams, then (1/4 x 20) = 30 grams remains
after 2 half-lives. It makes no difference what the substance is, or
how long its half-life is.
After another half-life . . . 1/2 of the half remains = 1/4 of the total original parent
If the original parent is 120 grams, then (1/4 x 20) = 30 grams remains
after 2 half-lives. It makes no difference what the substance is, or
how long its half-life is.