# ${m}_{P}$ and ${m}_{n}$ are masses of proton and neutron respectively. An element of mass m has Z protons and N neutrons, then  1. $m>Z{m}_{p}+N{m}_{n}$ 2. $m=Z{m}_{p}+N{m}_{n}$ 3. $m 4. m may be greater than, less than or equal to $Z{m}_{p}+N{m}_{n}$, depending on the nature of the element.

Subtopic:  Mass-Energy Equivalent |
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The nuclei  can be described as [1990]

1. isotones

2. isobars

3. isotopes of carbon

4. isotopes of nitrogen

Subtopic:  Mass-Energy Equivalent |
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The radioactivity of a sample is ${A}_{1}$ at a time ${t}_{1}$ and ${A}_{2}$ at time ${t}_{2}$.  If the mean life of the specimen is T, the number of atoms that have disintegrated in the time interval of ${t}_{2}-{t}_{1}$ is:

1. ${A}_{1}-{A}_{2}$

2. $\frac{{A}_{1}-{A}_{2}}{T}$

3. $\left({A}_{1}-{A}_{2}\right)T$

4. ${A}_{1}{t}_{1}-{A}_{2}{t}_{2}$

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What is the radius of iodine atom? (atomic no. 53, mass no. 126) [1988]

1.

2.

3.

4.

Subtopic:  Nuclear Binding Energy |
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Which of the following statements is true for nuclear forces? [1990]

1. They obey the inverse square law of distance.

2. They obey the inverse third power law of distance.

3. They are short range forces.

4. They are equal in strength to electromagnetic forces.

Subtopic:  Nuclear Binding Energy |
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The relationship between disintegration constant $\left[\lambda \right]$ and half-life [T] will be:

1.

2.

3.

4.

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Alpha particles are

1. 2 free protons

2. helium atoms

3. singly ionized helium atoms

4. doubly ionised helium atoms

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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?

1. 1.0 microcurie

2. 0.5 microcurie

3. 4 microcurie

4. 8 microcurie

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If the nuclear force between two protons, two neutrons and between a proton and a neutron is denoted by ${F}_{pp},$ ${F}_{nn}$ $and$ ${F}_{pn}$ respectively, then:

1. ${F}_{pp}\approx {F}_{nn}\approx {F}_{pn}$

2. ${F}_{pp}\ne {F}_{nn}$ $and$ ${F}_{pn}={F}_{nn}$

3. ${F}_{pp}={F}_{nn}={F}_{pn}$

4. ${F}_{pp}\ne {F}_{nn}\ne {F}_{pn}$

Subtopic:  Nuclear Energy |
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A radioactive element has half-life period 800 yr. After 6400 yr, what fraction will remain? [1989]

1. $\frac{1}{2}$

2. $\frac{1}{16}$

3. $\frac{1}{8}$

4.$\frac{1}{256}$