The half life period of radioactive element ${x}$ is same as the mean life time of another radioactive element $y.$ Initially they have the same number of atoms. Then:
${x}$-will decay faster than ${y}$.
${y}$ - will decay faster than ${x}$.
${x}$ and ${y}$ have same decay rate initially and later on different decay rate.
${x}$ and ${y}$ decay at the same rate always.
Half life of radioactive element depends upon
The rest mass of an electron as well as that of positron is $0.51\, MeV$. When an electron and positron are annihilate, they produce gamma-rays of wavelength(s)
Using a nuclear counter the count rate of emitted particles from a radioactive source is measured. At $t = 0$ it was $1600$ counts per second and $t = 8\, seconds$ it was $100$ counts per second. The count rate observed, as counts per second, at $t = 6\, seconds$ is close to
The '$rad$' is the correct unit used to report the measurement of
The half life $(T)$ and the disintegration constant $(\lambda )$ of a radioactive substance are related as