Solar energy is due to:

1. fusion reaction.

2. fission reaction.

3. combustion reaction.

4. chemical reaction.

Subtopic:  Nuclear Energy |
 66%
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At time t = 0, N1 nuclei of decay constant λ1 and N2 nuclei of decay constant λ2 are mixed. The decay rate of the mixture is:

1. -N1N2e-λ1+λ2t 

2. -N1N2 e-λ1+λ2t 

3. -N1λ1e-λ1t + N2λ2e-λ2t 

4. -N1λ1N2λ2e-λ1+λ2t

Subtopic:  Radioactivity (OLD NCERT) |
 52%
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A nucleus Xnm emits one α and two β-particles. The resulting nucleus is

1. Xnm-4 

2. Xn-2m-4   

3. Xn-4m-4 

4. None of these

Subtopic:  Types of Decay |
 68%
From NCERT
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The half-life period of a radioactive substance is 6 h.  If after 24 h, activity is 0.01 μCi, what was the initial activity? 

1. 0.04 μCi 

2. 0.08 μCi

3. 0.24 μCi 

4. 0.16 μCi

Subtopic:  Radioactivity (OLD NCERT) |
 67%
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The radius of a nucleus of a mass number A is directly proportional to [MH CET 1999; AMU (En.) 2001; UPSEAT 2004; DUMET 2010]

1. A3 

2. A 

3. A2/3

4. A1/3

Subtopic:  Nuclear Binding Energy |
 89%
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mP and mn are masses of proton and neutron respectively. An element of mass m has Z protons and N neutrons, then 

1. m>Zmp+Nmn

2. m=Zmp+Nmn

3. m<Zmp+Nmn

4. m may be greater than, less than or equal to Zmp+Nmn, depending on the nature of the element.

Subtopic:  Mass-Energy Equivalent |
 66%
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The nuclei C136 and N147 can be described as [1990]

1. isotones

2. isobars 

3. isotopes of carbon

4. isotopes of nitrogen

Subtopic:  Mass-Energy Equivalent |
 88%
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The radioactivity of a sample is A1 at a time t1 and A2 at time t2.  If the mean life of the specimen is T, the number of atoms that have disintegrated in the time interval of t2-t1 is:

1. A1-A2 

2. A1-A2T

3. A1-A2T

4. A1t1-A2t2

Subtopic:  Radioactivity (OLD NCERT) |
 52%
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What is the radius of iodine atom? (atomic no. 53, mass no. 126) [1988]

1. 2.5×10-11 m

2. 2.5×10-9 m

3. 7×10-9 m

4. 7×10-6 m

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 |
 80%
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