If one starts with one curie of radioactive substance ($T_{1/2}  = 12\,hrs$) the activity left after a period of $1$ week will be about

The nucleus $_{10}^{23} Ne$ decays by $\beta^{-}$ emission. Write down the $\beta$ -decay equation and determine the maximum kinetic energy of the electrons emitted. Given that

$m\left(_{10}^{23} Ne \right)=22.994466 \;u$

$m\left(_{11}^{23} Na\right) =22.089770\; u$

At $t = 0$, number of active nuclei in a sample is $N_0$. How much no. of nuclei will decay in time between its first mean life and second half life?

Write the law of radioactive decay.

The rate of disintegration of fixed quantity of a radioactive element can be increased by

A radioactive material decays by simultaneous emission of two particles with respective half lives $1620$ and $810$ years. The time (in years) after which one- fourth of the material remains is