Question

If the mean life of a radioactive substance is \[ \frac{20}{\ln4} \] minutes, then the ratio of the number of atoms remaining undecayed and the number of atoms decayed of the substance at a time of \(30\) minutes is

• A. \(3:8\)
• B. \(7:8\)
• C. \(1:7\)
• D. \(1:8\)

Hint:

For radioactive decay, \[ \boxed{ N=N_0e^{-\lambda t}, \qquad \lambda=\frac1{\tau}, } \] where \[ \boxed{\tau} \] is the mean life.

Answer 1

The Correct Option is C