Q. No.Alpha particles are
1. 2 free protons
2. helium atoms
3. singly ionized helium atoms
4. doubly ionised helium atoms
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
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. \(F_{p p} \neq F_{n n} \neq F_{p n}\)
A radioactive element has half-life period 800 yr. After 6400 yr, what fraction will remain? [1989]
1.
2.
3.
4.
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
1. \(\mathrm{Li}^7\)
2. \(\mathrm{Na}^{21}\)
3. \(\mathrm{S}^{16}\)
4. \(\mathrm{Ca}^{40}\)
Energy released in the fission of a single nucleus is 200 MeV. The fission rate of a filled reactor operating at a power level of 5 W is
1.
2.
3.
4.
| 1. | mass number reduced by \(2\) |
| 2. | mass number reduces by \(6\) |
| 3. | atomic number is reduced by \(2\) |
| 4. | atomic number remains unchanged |
Which of the following is used as a moderator in nuclear reactors?
1. Plutonium
2. Cadmium
3. Heavy water
4. Uranium
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