Beta rays emitted by a radioactive material are

Assertion: Cobalt-$60$ is useful in cancer therapy.
Reason: Cobalt-$60$ is a source of $\gamma$-radiations capable of killing cancerous cells.

Consider a $\beta$ decay reaction:
${}_1^3H \to {}_2^3He + {e^{ - 1}} + \bar v$
The atomic masses of ${}_1^3H$ and ${}_2^3He$ are $3.016050 \, u$ and $3.016030 \, u$,respectively. Find the maximum possible energy of the electron in $MeV$.

Which of the following will have the highest penetrating power?

$A$ radioactive material $P$ first decays into $Q$ and then $Q$ decays to non-radioactive material $R$. Which of the following figures represents the time-dependent mass of $P$,$Q$,and $R$?

Beta rays emitted by a radioactive material are