What fraction of a radioactive material will get disintegrated in a period of two half-lives?

1. whole

2. half

3. one-fourth

4. three-fourth

Subtopic:  Radioactivity (OLD NCERT) |
 56%
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If the nucleus A1327l has a nuclear radius of about 3.6 fm, then T52125e would have its radius approximately as [2007]

1. 6.0 fm 

2. 9.6 fm

3. 12.0 fm 

4. 4.8 fm

Subtopic:  Nuclear Binding Energy |
 82%
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After two hours, one-sixteenth of the starting amount of a certain radioactive isotope remained undecayed. The half life of the isotope is [Bihar MEE 1995; Manipal MEE 1995; MP PMT 1997; AFMC 2000, 05; DPMT 2002]

1. 15 minutes 

2. 30 minutes

3. 45 minutes

4. 1 hour

Subtopic:  Radioactivity (OLD NCERT) |
 82%
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PMT - 1997
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Atomic weight of boron is 10.81 and it has two isotopes B510 and B511. Then, the ratio of atoms of  B510 and B511 in nature would be 

1. 19 : 81

2. 10 : 11 

3. 15 : 16 

4. 81 : 19

Subtopic:  Mass-Energy Equivalent |
 61%
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The half-life of radium is 1600 yr.  The fraction of a sample of radium that would remain

after 6400 yr [1991]

1. 14   

2. 12 

3. 18 

4. 116

Subtopic:  Radioactivity (OLD NCERT) |
 81%
From NCERT
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The count rate of a Geiger Muller counter for the radiation of a radioactive material of half-life 30 min decreases to 5 s-1 after 2 h. The initial count rate was [1995]

1. 20 s-1 

2. 25 s-1 

3. 80 s-1 

4. 625 s-1

Subtopic:  Radioactivity (OLD NCERT) |
 69%
From NCERT
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An element A decays into element C by a two step process

AB+H2e4
BC+2e-

then  [1989]

1. A and C are isotopes

2. A and C are isobars

3. A and B are isotopes

4. A and B are isobars

Subtopic:  Types of Decay |
 66%
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The radius R of a nuclear matter varies with A as

1. R α A2/3

2. R α A1/3

3. R α A0 

4. R α A

Subtopic:  Mass-Energy Equivalent |
 95%
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Number of nuclei of a radioactive substance at time t = 0 are 2000 and 1800 at time t = 2s. Number of nuclei left after t = 6s is [MGIMS 2010]

1. 1442 

2. 1554 

3. 1652 

4. 1458

Subtopic:  Radioactivity (OLD NCERT) |
 61%
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In a radioactive material, the activity at time t1 is R1 and at a later time, t2 is R2. If the decay constant of the material is λ, then:

1. R1=R2e-λt1-t2   

2. R1=R2eλt1-t2

3. R1=R2t2t1 

4. R1=R2

Subtopic:  Radioactivity (OLD NCERT) |
 73%
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