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

1. 12

2. 116 

3. 18 

4.1256

Subtopic:  Radioactivity (OLD NCERT) |
 76%
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If a proton and anti-proton come close to each other and annihilate, how much energy will be released:

1. 1.5×10-10 J           

2. 3×10-10 J         

3. 4.5×10-10 J         

4. None of these

Subtopic:  Mass-Energy Equivalent |
From NCERT
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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 |
 66%
From NCERT
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The mass density of a nucleus varies with mass number A as [1992]

1. A2

2. A 

3. Constant 

4. 1A

Subtopic:  Nuclear Binding Energy |
 78%
From NCERT
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Energy released in the fission of a single U23592 nucleus is 200 MeV. The fission rate of a U23592 filled reactor operating at a power level of 5 W is 

1. 1.56×10-10 s-1 

2. 1.56×1011 s-1

3. 1.56×10-16 s-1   

4. 1.56×10-17 s-1

Subtopic:  Nuclear Energy |
 70%
From NCERT
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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 |
 78%
From NCERT
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Which of the following is used as a moderator in nuclear reactors? 

1. Plutonium 

2. Cadmium 

3. Heavy water

4. Uranium 

Subtopic:  Nuclear Energy |
 80%
From NCERT
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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 |
 67%
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The binding energy per nucleon of deuterium and helium atom is \(1.1\) MeV and \(7.0\) MeV. If two deuterium nuclei fuse to form a helium atom, the energy released is:
1. \(19.2\) MeV
2. \(23.6\) MeV
3. \(26.9\) MeV 
4. \(13.9\) MeV
Subtopic:  Nuclear Binding Energy |
 76%
From NCERT
PMT - 2001
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In a fission reaction,
\(^{236}_{92}\mathrm{U}\rightarrow ~^{117}\mathrm{X}~+~^{117}\mathrm{Y}~+~^1_0n~+~^1_0n,\) the binding energy per nucleon of \(\mathrm{X}\) and \(\mathrm{Y}\) is \(8.5\) MeV whereas that of \(^{236}\mathrm{U}\) is \(7.6\) MeV. The total energy liberated will be about:
1. \(2000\) MeV
2. \(200\) MeV
3. \(2\) MeV 
4. \(1\) keV

Subtopic:  Nuclear Binding Energy |
 77%
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