A radioactive sample with a half-life of 1 month has the label : ‘Activity = 2 microcurie on 1-8-1991’. What would be its activity two months earlier ?
A.
1.0 microcurie
B.
0.5 microcurie
C.
4 microcurie
D.
8 microcurie
Answer :
8 microcurie
Solution :
The activity of a radioactive substance is defined as the rate at which the nuclei of its atoms in the sample disintegrate. In two half-lives, the activity becomes one-fourth. Two months is 2 half-life period. The activity, two months earlier was
$$2 \times {2^2} = {\text{8}}\,{\text{microcurie}}{\text{.}}$$ NOTE
The activity of a radioactive sample is called one curie, if it undergoes $$3.7 \times {10^{10}}$$ disintegrations per second.
Releted MCQ Question on Modern Physics >> Atoms or Nuclear Fission and Fusion
In the nuclear fusion reaction
$$_1^2H + _1^3H \to _2^4He + n$$
given that the repulsive potential energy between the two
nuclei is $$ \sim 7.7 \times {10^{ - 14}}J,$$ the temperature at which the gases must be heated to initiate the reaction is nearly
[Boltzmann’s Constant $$k = 1.38 \times {10^{ - 23}}J/K$$ ]
The binding energy per nucleon of deuteron $$\left( {_1^2H} \right)$$ and helium nucleus $$\left( {_2^4He} \right)$$ is $$1.1\,MeV$$ and $$7\,MeV$$ respectively. If two deuteron nuclei react to form a single helium nucleus, then the energy released is