List of top Physics Questions on deccay rate

Radioactive material $'A'$ has decay constant $' 8 \lambda '$ and material $'B' $ has decay constant $'\lambda'$ Initially they have same number of nuclei. After what time, the ration of number of nuclei of material of material $'B' $ to that $'A'$ will be $\frac{1}{e} ?$
The half-life of a radioactive substance is $10$ days. This means that
1 curie is
The half-life of a radioactive element is $10 \,h$. The fraction of initial radioactivity of the element that will remain after $40\, h$ is
The half-life of $Ra ^{226}$ is 1620 years. Then the number of atoms decay in one second in $1 g$ of radium (Avogadro number $\left.=6.023 \times 10^{23}\right)$
The power obtained in a reactor using $U^{235}$ disintegration is $1000\, {kW}$. The mass decay of $U^{235}$ per hour is
Two radioactive nuclei $P$ and $Q$, in a given sample decay into a stable nucleus $R$. At time $t = 0$, number of $P$ species are $4\, N_0$ and that of $Q$ are $N_0$. Half-life of $P$ (for conversion to $R$) is $1$ minute where as that of $Q$ is $2$ minutes. Initially there are no nuclei of $R$ present in the sample. When number of nuclei of $P$ and $Q$ are equal, the number of nuclei of $R$ present in the sample would be
What is the age of an ancient wooden piece if it is known that the specific activity of $C^{14}$ nuclide in its amounts is $3/5$ of that in freshly grown trees? Given the half of $C$ nuclide is $5570\, yr$.
The decay constant of a radio isotope is $\lambda$. If $A_1$ and $A_2$ are its activities at times $t_1 $ and $t_2$ respectively, the number of nuclei which have decayed during the time $(t_1-t_2)$
Two radioactive materials $X_1$, and $X_2$ have decay constants 5$\lambda$ and $\lambda$ respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of X$_1$ to that X$_2$ will be 1/e after a time
Half-life of a radioactive substance A is 4 days. The probability that a nucleus will decay in two half-lives is
The half-life of radium is $1620\, yr$ and its atomic weight is $226\, kg$ per kilomol. The number of atoms that will decay from its $1\, g$ sample per second will be (Avogadro's number $N=6.023 \times 10^{23}$ atoms/ $mol$ )
After 280 days, the activity of a radioactive sample is 6000 dps. The activity reduces to 3000 dps after another 140 days. The initial activity of the sample in dps is
Half life of radioactive element is 12.5 Hour and its quantity is 256 gm. After how much time its quantity will remain 1 gm : -
Two radioactive materials $X_1$ and $X_2$ have decay constants $10\lambda$ and $\lambda$ respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of $X_1$ to that of $X_2$ will be 1/e after a time
In the nuclear reaction $ _{13}A{{l}^{27}}(d,\alpha )x,X $ is:
Half-life for radioactive $^{14}C$ is 5760 yr. In how many years, 200 mg of $^{14}C$ will be reduced to 25 mg?
The count rate of a Geiger Muller counter for the radiation of a radioactive material of half-life of 30 minutes decreases to 5 second$^{-1}$ after 2 hours. The initial count rate was
During a negative beta decay
If 10% of a radioactive material decays in 10 days the percentage of the material that decays in 20 days is
Two radioactive substances $A$ and $B$ have decay constants $5\lambda$ and $\lambda$ respectively. At $t = 0$, they have the same number of nuclei. The ratio of number of nuclei of $A$ to those of $B$ will be $(1/e)^{2}$ after a time interval
Two radioactive nuclei $A$ and $B$ are taken with their disintegration constant $\lambda_{A}$ and $\lambda_{B}$ and initially $N_{A}$ and $N_{B}$ number of nuclei are taken then the time after which their undisintegrated nuclei are same is
The decay constant of radium is $ 4.28 \times 10^{-4} $ per yr .Its half-life is approximately
The counting rate observed from a radioactive source at t = 0 seconds was 1600 counts per second and t = 8 seconds it was 100 count per second. The counting rate observed, as counts per second at t = 6 seconds will be :
The count rate from $100\, cm^{3}$ of a radioactive liquid is $c$. Some of this liquid is now discarded. The count rate of the remaining liquid is found to be $c/10$ after three half-lives. The volume of the remaining liquid, in $cm^{3}$, is