A radioactive element disintegrates for a time interval equal to its mean life

PHYSICS · Single correct · A Level · Physics · Nuclear physics · Nuclear physics

Problem

A radioactive element disintegrates for a time interval equal to its mean life. The fraction that has disintegrated is (1)

\frac{1}{e}

(2)

1-\frac{1}{e}

(3)

\frac{0.693}{e}

(4)

0.693\left(1-\frac{1}{e}\right)