The number of atoms remaining after every half-life:

$\overline{){\mathbf{N}}{\mathbf{=}}{{\mathbf{N}}}_{{\mathbf{0}}}{{\mathbf{\left(}}\frac{\mathbf{1}}{\mathbf{2}}{\mathbf{\right)}}}^{\mathbf{(}\mathbf{t}\mathbf{/}{\mathbf{t}}_{\mathbf{1}\mathbf{/}\mathbf{2}}\mathbf{)}}}$

After 2 hours:

N = N_{0}(1/2)^{(2/2)} = 0.5N_{0}

A container holds a pure sample of a radioactive substance with a half-life of 2 hours.

Which of the following statements are true?

a) After 1 hour, less than 50% of the original atoms in the container will have decayed.

b) After 1 hour, more than 50% of the original atoms in the container will have decayed.

c) After 2 hours, 50% of the original atoms in the container will have decayed.

d) After 4 hours, 25% of the original atoms will have decayed.

e) After 4 hours, the total number of atoms in the container will be reduced by 75%.

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