A radioactive substance disintegrates 1/64 of initial value in 60 s. The half-life of this substance is

1. 5 s 

2. 10 s

3. 30 s 

4. 20 s

Subtopic:  Radioactivity (OLD NCERT) |
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The nucleus C612 absorbs an energetic neutron and emits a beta particle β-. The resulting nucleus is 

1. C714

2. N713 

3. B513 

4. C613

Subtopic:  Types of Decay |
 69%
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If in a nuclear fusion  process, the masses of the fusion nuclei be m1 and m2 and the mass of the resultant nucleus be m3, then [2004]

1. m3=m1+m2

2. m3=m1-m2

3. m3<m1+m2 

4. m3>m1+m2

Subtopic:  Mass-Energy Equivalent |
 81%
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The nuclei of which one of the following pairs of nuclei are isotones? [2005]

1. S34e74, G31a71 

2. M42o92, Z40r92

3. S38r84, S38r86 

4. C20a40, S3216

Subtopic:  Nuclear Binding Energy | Mass-Energy Equivalent |
 87%
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The counting rate observed from a radioactive source at t = 0 second was 1600 counts per second and at t = 8 seconds it was 100 counts per second. The counting rate observed, as counts per second, at t = 6 seconds will be:

1. 400

2. 300

3. 200

4. 150

Subtopic:  Radioactivity (OLD NCERT) |
 68%
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If N0 is the original mass of the substance of half life period T1/2= 5 years, then the amount of substance left after 15 years is [AIEEE 2012]

1. N0/8 

2. N0/16

3. N0/2

4. N0/4

Subtopic:  Radioactivity (OLD NCERT) |
 88%
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The numbers of nuclei of a radioactive substance at time t = 0 are 1000 and 900 at time t = 2 sec. Then the number of nuclei at time t = 4 sec will be:

1. 800

2. 810 

3. 790 

4. 700

Subtopic:  Radioactivity (OLD NCERT) |
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PMT - 2010
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A nucleus XZA has mass represented by m(A, Z). If mp and mn denote the mass of proton and neutron respectively and BE is the binding energy (in MeV), then:
[2007]

1. BE = [m(A, Z) - Zmp- (A - Z)mnc2

2. BE = [Zmp+ (A - Z)mn- m(A,Z)] c2

3. BE = [Zmp+ Amn- m(A, Z)] c2

4. BE = m(A, Z) - Zmp- (A, Z)mn

Subtopic:  Nuclear Binding Energy |
 84%
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Half-lives of two radioactive substances A and B respectively are 20 min and 40 min.  Initially, the samples of A and B have an equal number of nuclei. After 80 min the ratio of the remaining number of A and B nuclei is:

1. 1 : 16

2. 4 : 1

3. 1 : 4 

4. 1 : 1

Subtopic:  Radioactivity (OLD NCERT) |
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Radioactive C2760o is transformed into stable N2860i by emitting two γ-rays of energies

1. 1.33 MeV and 1.17 MeV in succession

2. 1.17 MeV and 1.33 MeV in succession

3. 1.37 MeV and 1.13 MeV in succession

4. 1.17 MeV and 1.13 MeV in succession

Subtopic:  Radioactivity (OLD NCERT) |
 59%
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