A freshly prepared radioactive source of half-life 2 hrs. emits radiations of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with the source is

1.  6 hrs.

2.  12 hrs.

3.  24 hrs.

4.  128 hrs.  

Subtopic:  Radioactivity (OLD NCERT) |
 85%
From NCERT
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If the binding energy per nucleon in Li73 and He42 nuclei are respectively 5.60 MeV and
7.06 MeV, then the energy of proton in the reaction Li72 + p 22He4 is :

1.  19.6 MeV

2.  2.4 MeV

3.  8.4 MeV

4.  17.3 MeV

Subtopic:  Nuclear Binding Energy | Mass-Energy Equivalent |
 68%
From NCERT
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In the equation AI1327 + He24  P1530 + X where X is-

1.  P11 

2.  H12 

3.  He24 

4.  n01

Subtopic:  Mass-Energy Equivalent |
 93%
From NCERT
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If the nuclear radius of A27l is 3.6 Fermi, the approximate nuclear radius of C64u in Fermi is

1. 2.4                                       

2. 1.2

3. 4.8                                       

4. 3.6

Subtopic:  Mass-Energy Equivalent |
 86%
From NCERT
NEET - 2012
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The half-life of a radioactive isotope X is 50 yr.

It decays to another element Y which is stable.

The two elements X and Y were found to be in 

the ratio of 1:15 in a sample of a given rock.

The age of rock was estimated to be

1. 200 yr

2. 250 yr

3. 100 yr

4. 150 yr

Subtopic:  Radioactivity (OLD NCERT) |
 73%
From NCERT
NEET - 2011
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Fusion reaction takes place at a higher temperature because:

1. atoms get ionized at high temperatures.
2. kinetic energy is high enough to overcome the Coulomb repulsion between nuclei.
3. molecules break up at a high temperature.
4. nuclei break up at a high temperature.
Subtopic:  Nuclear Energy |
 81%
From NCERT
NEET - 2011
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The decay constant of a radio isotope is λ. If A1 and A2 are its activities at times t1 and t2 respectively, the number of nuclei which have decayed during the time (t1-t2)

1. A1t1-A2t2                                       

2. A1-A2

3. (A1-A2)λ                                       

4. λ(A1-A2) 

Subtopic:  Types of Decay |
 73%
From NCERT
NEET - 2010
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The binding energy per nucleon in deuterium and helium nuclei are 1.1 MeV and 7.0 MeV, respectively. When two deuterium nuclei fuse to form a helium nucleus the energy released in the fusion is 

1. 23.6 MeV                                         

2. 2.2 MeV

3. 28.0 MeV                                         

4. 30.2 MeV

Subtopic:  Nuclear Binding Energy |
 89%
From NCERT
NEET - 2010
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Two radioactive material X1 and X2 have decay constants 5λ and λ respectively. If initially they have the same number of nuclei of X1to that of X2 will be 1eafter a time 

1. λ                                     

2. 12λ

3. 14λ                                 

4. eλ

Subtopic:  Radioactivity (OLD NCERT) |
 80%
From NCERT
NEET - 2008
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One nanogram of matter converted into energy will give- 

1. 90 J                     

2. 9×103 J 

3. 9×1010 J            

4. 9×104 J

Subtopic:  Nuclear Binding Energy |
From NCERT
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