After 280 days, activity of a radioactive sample is 6000, dps . activity reduces to 3000, dps after

English

Gujarati

Hindi

13.Nuclei

medium

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

A

$6000$

B

$9000$

C

$3000$

D

$24000$

(IIT-2004)

Solution

(d) Here the activity of the radioactive sample reduces to half in $140 \,days$.

Therefore, the half life of the sample is $140 \,days.$

$280\, days$ is it’s two half lives.

So before two half lives it’s activity was $({2^2} \times $ present activity).

$\therefore$ Initial activity = ${2^2} \times 6000 = 24000\,dps.$

Standard 12

Physics

Share

Similar Questions

Radioactivity is

easy

After $3$ hours, only $0.25 \,mg$ of a pure radioactive material is left. If initial mass was $2 \,mg$ then the half life of the substance is …… $hr$

easy

A sample which has half life of $10^{33}$ year, if initial number of nuclei of the sample is $26 \times 10^{24}$. Then the number of nuclei decayed in $1$ year is ……….. $ \times 10^{-7}$

medium

(AIIMS-2019)

A radioactive nucleus ${ }_{\mathrm{Z}}^{\mathrm{A}} \mathrm{X}$ undergoes spontaneous decay in the sequence

${ }_{\mathrm{Z}}^{\mathrm{A}} \mathrm{X} \rightarrow {}_{\mathrm{Z}-1}{\mathrm{B}} \rightarrow {}_{\mathrm{Z}-3 }\mathrm{C} \rightarrow {}_{\mathrm{Z}-2} \mathrm{D}$, where $\mathrm{Z}$ is the atomic number of element $X.$ The possible decay particles in the sequence are :

medium

(NEET-2021)

Half-life of a radioactive substance is $20$ minutes. Difference between points of time when it is $33\%$ disintegrated and $67\%$ disintegrated is approximately ……….. $min$

hard

(AIIMS-2000)