The half-life of a radioactive substance is  30 minutes. The time (in minute) taken between 40% decay and 85% decay of the same radioactive substance is

(1) 15           

(2) 30

(3) 45           

(4) 60

Subtopic:  Radioactivity (OLD NCERT) |
 58%
From NCERT
NEET - 2016
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If the radius of the 13Al27 nucleus is taken to RAl then the radius of 53Te125 nucleus is nearly

1. (53/13)1/3 RAl

2. 5/3 RAl

3. 3/5 RAl

4. (13/53)1/3 RAl

 76%
From NCERT
NEET - 2015
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A nucleus of uranium decays at rest into nuclei of thorium and helium. Then,

(1) the helium nucleus has more kinetic energy than the thorium nucleus

(2) the helium nucleus has less momentum than the thorium nucleus

(3) the helium nucleus has more momentum than the thorium nucleus

(4) the helium nucleus has less kinetic energy than the thorium nucleus

Subtopic:  Radioactivity (OLD NCERT) |
 67%
From NCERT
NEET - 2015
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The binding energy per nucleon of  Li37 and He24 nuclei are 5.60meV and 7.06meV, respectively. 
In the nuclear reaction Li37  + H11  He24 + He24 + Q  , the value of energy Q released is -

(a)19.6MeV

(b)-2.4MeV

(c)8.4MeV

(d)17.3MeV

Subtopic:  Nuclear Binding Energy |
 62%
From NCERT
NEET - 2014
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A radioisotope X with a half-life 1.4x109 yr decays into Y which is stable. A sample of the rock from a cave was found to contain X and Y in the ratio 1:7. The age of the rock is

(1)1.96x109 yr

(2)3.92x109 yr

(3)4.20x109 yr

(4)8.40x10yr

Subtopic:  Radioactivity (OLD NCERT) |
 73%
From NCERT
NEET - 2014
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A certain mass of hydrogen is changed to helium by the process of fusion. The mass defect in the fusion reaction is 0.02866 u. The energy liberated per nucleon is: (given 1 u = 931 MeV)

(1) 2.67 MeV
 

(2) 26.7 MeV
 

(3) 6.675 MeV
 

(4) 13.35 MeV

Subtopic:  Nuclear Binding Energy |
From NCERT
NEET - 2013
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If the nuclear radius of A27l is 3.6 Fermi, the approximate nuclear radius of C64u in Fermi is

(a)2.4                                         (b)1.2

(c)4.8                                         (d)3.6

Subtopic:  Mass-Energy Equivalent |
 85%
From NCERT
NEET - 2012
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A mixture consists of two radioactive materials A1 and A2 with half lives of 20 s and 10 s respectively.Initially the mixture has 40g of A1 and 160g of A2. The amount of the two in the mixture will become equal after

(a)60 s                                      (b)80 s

(c)20 s                                      (d) 40 s

Subtopic:  Radioactivity (OLD NCERT) |
 67%
From NCERT
NEET - 2012
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The half-life of a radioactive nucleus is 50 days. The time interval (t2-t1) between the time t2 when 23 of it has decayed and the time t1 when 13 of it had decayed is:

1. 30 days

2. 50 days

3. 60 days

4. 15 days

Subtopic:  Radioactivity (OLD NCERT) |
 76%
From NCERT
NEET - 2012
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Fusion reaction takes place at high temperature because

(1) atoms get ionised at high temperature 

(2) kinetic energy is high enough to overcome the Coulomb repulsion between nuclei

(3) molecules break up at high temperature

(4) nuclei break up at high temperature

Subtopic:  Mass-Energy Equivalent | Nuclear Energy |
 79%
From NCERT
NEET - 2011
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