Which statement is correct?
property | $\alpha$-particle | $\beta$-particle | $\gamma$-ray |
nature | 2 protons + 2 neutrons | an electron | electromagnetic wave |
masss | $4\:$u | $0.00055\:$u | $0$ |
speed | 5 % the speed of light | 98 % the speed of light | speed of light |
The following count rate from a radioactive source was measured.
$t$ in s | 0 | 30 | 60 | 90 | 120 |
count rate in 1/s | 160 | 110 | 71 | 47 | 32 |
atomic nucleus | The central area of an atom, consisting of protons and neutrons. |
nuclide | An atom with specific number of protons and neutrons. |
radioactivity | Radioactivity refers to the property of an unstable nucleus by emitting ionized rays and particles. |
radioactive decay | The nucleus is changing into a different nucleus while emitting quantum like alpha-, beta- particles or gamma-rays. |
count rate$C$ | The number of measured radioactive particles per second. |
exponential decay | If a radioactive material undergoes decay the number of nuclei $N$ decreases by an exponential function $N(t)=N_0\cdot e^{-\lambda t}$. $N_0$ the initial number of nuclei, $\lambda$ the decay constant. The count rate $C$ or the activity $A$ also follow this law. |
decay constant $\lambda$ in 1/s | $1/\lambda$ is the time where the number of nuclei is reduced by 37 %. It also refers to the initial gradient of the decay-graph. |
half life $t_{1/2}$ | The half life $t_{1/2}$ refers to the time where the numbers of nuclei are divided by two. |
applications of radioactivity | nuclear power plants, X-rays, determine the age of rocks - carbon dating, radio therapy |