List of top Physics Questions on Radioactive Decay

The number of undecayed nuclei \( N \) in a sample of radioactive material as a function of time \( t \) is shown in the figure. Which of the following graphs correctly shows the relationship between \( N \) and the activity \( A \)? 

A radioactive nucleus decays as follows: \[ X \xrightarrow{\alpha} X_1 \xrightarrow{\beta^-} X_2 \xrightarrow{\alpha} X_3 \xrightarrow{\gamma} X_4 \] If the mass number and atomic number of \( X_4 \) are 172 and 69 respectively, then the atomic number and mass number of \( X \) are
A radioactive material P first decays into Q and then Q decays to non-radioactive material R. Which of the following figure represents time dependent mass of P, Q and R?
A radioactive nucleus \( n_2 \) has 3 times the decay constant as compared to the decay constant of another radioactive nucleus \( n_1 \). If the initial number of both nuclei are the same, what is the ratio of the number of nuclei of \( n_2 \) to the number of nuclei of \( n_1 \), after one half-life of \( n_1 \)?
A radioactive nucleus decays as follows: \[ X \to X_1 \to X_2 \to X_3 \to X_4 \] If the mass number and atomic number of \( X_4 \) are 172 and 69 respectively, the mass number and atomic number of \( X \) are:
Which one of the following is not a type of radioactive decay?
If the half-life of a radioactive material is 10 years, then the percentage of the material decayed in 30 years is
If the time taken for a radioactive substance to decay 8% to 77% is 12 minutes, then the half life of the substance in minutes is
If the half-life of \( D \) is 1500 years and \( B \) is 2000 years, what is the mean lifetime?
The natural logarithm of the activity \( R \) of a radioactive sample varies with time \( t \) as shown. At \( t = 0 \), there are \( N_0 \) undecayed nuclei. Then \( N_0 \) is equal to \([\text{Take} \ e^{7.5}] \)
natural logarithm
Dimensional formula for activity of a radioactive substance is
The half-life period of a radioactive element A is 62 years. It decays into another stable element B. An archaeologist found a sample in which A and B are in 1 : 15 ratio. The age of the sample is:
A and B are two radioactive samples of half-life 12 hours and 16 hours respectively. The number of nuclei in them are in the ratio 2:1. After 48 hours, this ratio will become
Consider two radioactive materials A and B. When A decays into 6.25 percent of its original amount, B decays into 25 percent of its original amount. The ratio of their decay constants \( \lambda_A \) and \( \lambda_B \) is:
In the uranium radioactive series the initial nucleus is \(^{238}U\) and the final nucleus is \(^{206}Pb\). When the uranium nucleus decays to lead, the number of \(\alpha\)-particles and \(\beta\)-particles emitted respectively are:
The relation between the mean life time \( \tau \) and the half life time \( T_{1/2} \) of a radioactive substance is:
Disintegration rate of a radio-active sample is \( 10^{10} \) per hour at 20 hours from the start. It reduces to \( 5 \times 10^9 \) per hour after 30 hours. Calculate the decay constant.
A radioactive element A with half life 3 hours decays to a stable element B. After a time $ t $, the ratio of A and B atoms is 1:16 then the time $ t $ in hours is
Which of the following statement is true when a gamma decay occurs from the nucleus of an atom?
An atomic nucleus X with half-life \( T_X \) decays to a nucleus Y, which has half-life \( T_Y \). The condition(s) for secular equilibrium is/are
In a typical human body, the amount of radioactive \(^{40}K\) is \(3.24 \times 10^{-5}\) percent of its mass. The activity due to \(^{40}K\) in a human body of mass 70 kg is .................. kBq.