Atoms have different atomic numbers as well as different mass numbers but have the same number of neutrons is called:
1. isotopes
2. isobars
3. isotones
4. isodiaphers

Subtopic:  Nucleus |
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In a radioactive substance at t = 0, the number of atoms is 8$×{10}^{4}$, its half-life period is 3 yr. The number of atoms equal to $1×{10}^{4}$ will remain after an interval of:

1. 9 yr

2. 8 yr

3. 6 yr

4. 24 yr

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PMT - 2010
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What is the respective number of $\alpha$ and $\beta$-particles emitted in the following radioactive decay?

1. 6 and 8

3. 6 and 6

3. 8 and 8

4. 8 and 6

Subtopic:  Types of Decay |
73%
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The half-life of radium is 1622 years. How long will it take for seven-eighth of a given amount of radium to decay

1. 3244 years

2. 6488 years

3. 4866 years

4. 811 years

72%
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PMT - 1999
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The mass of a proton is 1.0073 u and that of the neutron is 1.0087 u (u = atomic mass unit) The binding energy of ${}_{2}H{e}^{4}$ is (mass of helium nucleus = 4.0015 u)

1. 28.4 MeV

2. 0.061 u

3. 0.0305 J

4. 0.0305 erg

Subtopic:  Mass-Energy Equivalent |
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The binding energies of the nuclei A and B are  respectively. Three atoms of the element B fuse to give one atom of element A and an energy Q is released. Then  and Q are related as:

1. ${E}_{a}-3{E}_{b}=Q$

2. $3{E}_{b}-{E}_{a}=Q$

3. ${E}_{a}+3{E}_{b}=Q$

4. ${E}_{b}+3{E}_{a}=Q$

Subtopic:  Nuclear Binding Energy |
52%
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A free neutron decays into a proton, an electron and:

1. A beta particle.

2. An alpha particle.

3. An antineutrino.

4. A neutrino.

Subtopic:  Types of Decay |
64%
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In a radioactive sample the fraction of initial number of radioactive nuclei, which remains undecayed after n mean lives is:

1. $\frac{1}{{e}^{n}}$

2.  ${e}^{n}$

3. $1-\frac{1}{{e}^{n}}$

4. ${\left(\frac{1}{e-1}\right)}^{n}$

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The activity of a radioactive sample is measured as 9750 counts/min at t = 0 and as 975 counts/min at t = 5 min. The decay constant is approximately:

1. 0.922/min

2. 0.691/min

3. 0.461/min

4. 0.230/min

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The energy equivalent of one atomic mass unit is:
1. $$1.6\times 10^{-19}~\text{J}$$
2. $$6.02\times 10^{23}~\text{J}$$
3. $$931~\text{MeV}$$
4. $$9.31~\text{MeV}$$

Subtopic:  Mass-Energy Equivalent |
82%
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