In a given reaction,

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Radioactive radiations are emitted in the sequence of  

1.  α, β, γ 

2. γ, α, β 

3. β, α, γ 

4. γ, β, α

Subtopic:  Radioactivity (OLD NCERT) | Types of Decay |
 90%
From NCERT
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An observer A sees an asteroid with a radioactive element moving by at a speed = 0.3 c and measures the radioactivity decay time to be TA. Another observer B is moving with the asteroid and measures its decay time as TB. Then TA and TB are related as below [VITEEE 2008]

1. TB < TA

2. TB = TA

3. TB > TA

4. Either 1 or 3 depending on whether the asteroid is approaching or moving away from A.

 

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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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A sample of radioactive element has a mass of 10 g at an instant t = 0. The approximate mass of this element in the sample after two mean lives is [2003]

1. 3.70 g

2. 6.30 g

3. 1.35 g

4. 2.50 g

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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%
From NCERT
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