NEET PYQs for Deccay Rate with Solutions: Practice NEET Previous Year Questions

Updated on - Jan 19, 2026

Deccay Rate is an important topic in the Physics section in NEET exam. Practising this topic will increase your score overall and make your conceptual grip on NEET exam stronger.

This article gives you a full set of NEET PYQs for Deccay Rate with explanations for effective preparation. Practice of NEET Physics PYQs including Deccay Rate questions regularly will improve accuracy, speed, and confidence in the NEET 2026 exam.

NEET PYQs for Deccay Rate with Solutions

1.
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
- $2\,N_0$
- $3\,N_0$
- $\frac{9\,N_0}{2}$
- $\frac{5\,N_0}{2}$
View Solution
2.
The power obtained in a reactor using $U^{235}$ disintegration is $1000\, {kW}$. The mass decay of $U^{235}$ per hour is
- 10 microgram
- 20 microgram
- 40 microgram
- 1 microgram
View Solution
3.
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 $\frac{1}{e} ?$
- $\frac{1}{7 \lambda} $
- $\frac{1}{8 \lambda} $
- $\frac{1}{9 \lambda} $
- $\frac{1}{ \lambda} $
View Solution
4.
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
- $1/4\lambda$
- e/$\lambda$
- $\lambda$
- $\frac{1}{2}\lambda$
View Solution
5.
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
- 80 second$^{-1}$
- 625second $^{-1}$
- 20second $^{-1}$
- 25 second $^{-1}$
View Solution
6.
Half-life for radioactive $^{14}C$ is 5760 yr. In how many years, 200 mg of $^{14}C$ will be reduced to 25 mg?
- 5760 yr
- 11520 yr
- 17280 yr
- 23040 yr
View Solution
7.
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 $(t_1-t_2)$
- $A_1t_1-A_2t_2$
- $A_1-A_2$
- $(A_1-A_2)/ \lambda$
- $\lambda (A_1-A_2)$
View Solution
8.
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 : -
- 50 Hrs
- 100 Hrs
- 150 Hrs
- 200 Hrs
View Solution

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NEET PYQs for Deccay Rate with Solutions

2.The power obtained in a reactor using $U^{235}$ disintegration is $1000\, {kW}$. The mass decay of $U^{235}$ per hour is

3.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 $\frac{1}{e} ?$

4.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

5.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

6.Half-life for radioactive $^{14}C$ is 5760 yr. In how many years, 200 mg of $^{14}C$ will be reduced to 25 mg?

7.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 $(t_1-t_2)$

8.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 : -

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2.
The power obtained in a reactor using $U^{235}$ disintegration is $1000\, {kW}$. The mass decay of $U^{235}$ per hour is

3.
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 $\frac{1}{e} ?$

4.
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

5.
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

6.
Half-life for radioactive $^{14}C$ is 5760 yr. In how many years, 200 mg of $^{14}C$ will be reduced to 25 mg?

7.
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 $(t_1-t_2)$

8.
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 : -