# 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. $$F_{p p} \approx F_{n n} \approx F_{p n}$$
2. $$F_{p p} \neq F_{n n}$$ and $$F_{p n} = F_{n n}$$
3. $$F_{p p} = F_{n n} = F_{p n}$$
4. $$F_{p p} \neq F_{n n} \neq F_{p n}$$
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.$\frac{1}{256}$

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If a proton and anti-proton come close to each other and annihilate, how much energy will be released:

1.

2.

3.

4. None of these

Subtopic:  Mass-Energy Equivalent |
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The stable nucleus that has a radius half of the radius of $$\mathrm{Fe}^{56}$$ is:
1. $$\mathrm{Li}^7$$
2. $$\mathrm{Na}^{21}$$
3. $$\mathrm{S}^{16}$$
4. $$\mathrm{Ca}^{40}$$

Subtopic:  Nucleus |
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The mass density of a nucleus varies with mass number A as [1992]

1. ${A}^{2}$

2. A

3. Constant

4. $\frac{1}{A}$

Subtopic:  Nuclear Binding Energy |
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Energy released in the fission of a single ${}_{92}U_{235}$ nucleus is 200 MeV. The fission rate of a ${}_{92}U_{235}$ filled reactor operating at a power level of 5 W is

1.

2.

3.

4.

Subtopic:  Nuclear Energy |
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In one $$\alpha \text-$$ and $$2\beta^{-} \text-$$emissions:
 1 mass number reduced by $$2$$ 2 mass number reduces by $$6$$ 3 atomic number is reduced by $$2$$ 4 atomic number remains unchanged
Subtopic:  Types of Decay |
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Which of the following is used as a moderator in nuclear reactors?

1. Plutonium

3. Heavy water

4. Uranium

Subtopic:  Nuclear Energy |
80%
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Heavy water is used as a moderator in a nuclear reactor. The function of the moderator is

1. to control energy released in the reactor

2. to absorb neutrons and stop the chain reaction

3. to cool the reactor

4. to slow down the neutrons to thermal energies

Subtopic:  Nuclear Energy |
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