a 280 days old radioactive substance shows an activity of

A 280 days old radioactive substance shows an activity of $$6000\,dps,$$ 140 days later its activity becomes $$3000\,dps.$$ What was its initial activity?

A. $$20000\,dps$$

B. $$24000\,dps$$

C. $$12000\,dps$$

D. $$6000\,dps$$

Answer : $$24000\,dps$$

Solution :
In two half lives, the activity will remain $$\frac{1}{4}$$ of its initial activity.

Releted MCQ Question on
Modern Physics >> Radioactivity

Releted Question 1

An alpha particle of energy $$5\,MeV$$ is scattered through $${180^ \circ }$$ by a fixed uranium nucleus. The distance of closest approach is of the order of

A. $$1\, \mathop {\text{A}}\limits^ \circ $$

B. $${10^{ - 10}}cm$$

C. $${10^{ - 12}}cm$$

D. $${10^{ - 15}}cm$$

View Answer

Releted Question 2

Beta rays emitted by a radioactive material are

A. electromagnetic radiations

B. the electrons orbiting around the nucleus

C. charged particles emitted by the nucleus

D. neutral particles

View Answer

Releted Question 3

Consider $$\alpha $$ particles, $$\beta $$ particles and $$\gamma $$ - rays, each having an energy of $$0.5\,MeV.$$ In increasing order of penetrating powers, the radiations are:

A. $$\alpha ,\beta ,\gamma $$

B. $$\alpha ,\gamma ,\beta $$

C. $$\beta ,\gamma ,\alpha $$

D. $$\gamma ,\beta ,\alpha $$

View Answer

Releted Question 4

A radioactive material decays by simultaneous emission of two particles with respective half-lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains is

A. 1080

B. 2430

C. 3240

D. 4860

View Answer

A 280 days old radioactive substance shows an activity of $$6000\,dps,$$ 140 days later its activity becomes $$3000\,dps.$$ What was its initial activity?

Releted MCQ Question on
Modern Physics >> Radioactivity

An alpha particle of energy $$5\,MeV$$ is scattered through $${180^ \circ }$$ by a fixed uranium nucleus. The distance of closest approach is of the order of

Beta rays emitted by a radioactive material are

Consider $$\alpha $$ particles, $$\beta $$ particles and $$\gamma $$ - rays, each having an energy of $$0.5\,MeV.$$ In increasing order of penetrating powers, the radiations are:

A radioactive material decays by simultaneous emission of two particles with respective half-lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains is

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Radioactivity

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A 280 days old radioactive substance shows an activity of $$6000\,dps,$$ 140 days later its activity becomes $$3000\,dps.$$ What was its initial activity?

Releted MCQ Question on Modern Physics >> Radioactivity

An alpha particle of energy $$5\,MeV$$ is scattered through $${180^ \circ }$$ by a fixed uranium nucleus. The distance of closest approach is of the order of

Beta rays emitted by a radioactive material are

Consider $$\alpha $$ particles, $$\beta $$ particles and $$\gamma $$ - rays, each having an energy of $$0.5\,MeV.$$ In increasing order of penetrating powers, the radiations are:

A radioactive material decays by simultaneous emission of two particles with respective half-lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains is

Practice More Releted MCQ Question on Radioactivity

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Releted MCQ Question on
Modern Physics >> Radioactivity

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Radioactivity