Atoms have different atomic numbers as well as different mass numbers but have the same number of neutrons is called:

1. isotopes  2. isobars
3. isotones 4. isodiaphers

Subtopic:  Nucleus |
 79%
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The binding energies of the nuclei A and B are Ea and Eb respectively. Three atoms of the element B fuse to give one atom of element A and an energy Q is released. Then Ea, Eb and Q are related as:

1. Ea-3Eb=Q 

2. 3Eb-Ea=Q

3. Ea+3Eb=Q 

4. Eb+3Ea=Q

Subtopic:  Nuclear Binding Energy |
 52%
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A free neutron decays into a proton, an electron and:

1. A beta particle.

2. An alpha particle.

3. An antineutrino.

4. A neutrino.

Subtopic:  Types of Decay |
 64%
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In a radioactive sample the fraction of initial number of radioactive nuclei, which remains undecayed after n mean lives is:

1. 1en 

2.  en   

3. 1-1en 

4. 1e-1n

Subtopic:  Radioactivity (OLD NCERT) |
 54%
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The activity of a radioactive sample is measured as 9750 counts/min at t = 0 and as 975 counts/min at t = 5 min. The decay constant is approximately:

1. 0.922/min           

2. 0.691/min         

3. 0.461/min           

4. 0.230/min

Subtopic:  Radioactivity (OLD NCERT) |
 54%
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Fission of nuclei is possible because the binding energy per nucleon in them [2005]

1. increases with mass number at high mass number

2. decreases with mass number at high mass

3. increases with mass number at low mass numbers

4. decreases with mass number at low mass number

Subtopic:  Nuclear Binding Energy |
 54%
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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%
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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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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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