輻射與放射性

The speeds of X-rays, $\gamma$ rays and $\beta$ rays in air are denoted by $v_X$, $v_\gamma$ and $v_\beta$ respectively. Which of the following is true ?

The corrected count rate of a sample of radioactive material was measured on the first day of each month. The readings on July 1 and September 1 are $0.8$ and $0.2$ counts per second respectively. What is the half-life of the radioactive material ?

$S$ is a radioactive source which emits radiation as it decays. If all the radiation emitted is bent by a magnetic field in the direction shown, then the radiation consists of

The half-life of a radioactive substance is $8$ hours. Its initial mass is $3$ g. Find the amount of the radioactive substance remaining unchanged after $24$ hours.

If the three kinds of radiations $\alpha$, $\beta$ and $\gamma$ are arranged in ascending order of their ionization power, their order is

In a $\beta$ decay, element $X$, having a half-life of $3$ days, decays into a stable element $Y$. If the initial mass of $X$ is $4$ g, what will be the masses of $X$ and $Y$ after $6$ days ?