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) |
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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

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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 |
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NEET - 2014
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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 |
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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) |
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From NCERT
NEET - 2012
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Two radioactive nuclei P and Q, in a given sample decay into a stable nucleus R. At time t=0, the number of P species are 4N0 and that of Q is N0Half-life of P(for conversion to R) is 1 min whereas that of Q is 2 min. Initially there are no nuclei of R present in the sample. When number of nuclei of P and Q are equal, the number of nuclei of R present in the sample would be: 

1. 3N0                                         

2. 9N02

3. 5N02                                       

4. 2N0

Subtopic:  Radioactivity (OLD NCERT) |
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NEET - 2011
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The activity of a radioactive sample is measured as N0 counts per minute at t=0 and N0/e counts per minute at t=5 min.The time (in minute) at which the activity reduces to half its value is 

(1) loge2/5                                                         

(2) 5loge 2

(3) 5 log10 2                                                         

(4) 5 loge 2

Subtopic:  Radioactivity (OLD NCERT) |
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From NCERT
NEET - 2010
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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) is:

1. A1t1-A2t2                                       

2. A1-A2

3. (A1-A2)λ                                         

4. λ(A1-A2) 

Subtopic:  Radioactivity (OLD NCERT) |
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From NCERT
NEET - 2010
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Two nuclei have their mass numbers in the ratio of 1:3. The ratio of their nuclear densities would be 

(1) 1:3

(2) 3:1

(3) 31/3:1

(4) 1:1

Subtopic:  Mass-Energy Equivalent |
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From NCERT
NEET - 2008
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Radioactive material 'A' has decay constant '8\(\lambda\)' and material 'B' has a decay constant '\(\lambda\)'. Initially, they have the same number of nuclei. After what time, the ratio of the number of nuclei of material 'A' to that of 'B' will be \(\frac{1}{e}\)?

\(1 .   \frac{1}{7 \lambda}\)
\(2 .   \frac{1}{8 \lambda}\)
\(3 .   \frac{1}{9 \lambda}\)
\(4 .   \frac{1}{\lambda}\)

Subtopic:  Radioactivity (OLD NCERT) |
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NEET - 2017
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