The nuclei of which one of the following pairs of nuclei are isotones? 

1. S34e74, G31a71 

2. M42o92, Z40r92

3. S38r84, S38r86 

4. C20a40, S3216

Subtopic:  Nuclear Binding Energy | Mass-Energy Equivalent |
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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) |
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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

1. N0/8 

2. N0/16

3. N0/2

4. N0/4

Subtopic:  Radioactivity (OLD NCERT) |
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The mass number of He is 4 and that for sulphur is 32. The radius of sulphur nucleus is larger than that of helium, by times

1. 8 

2. 4

3. 2 

4.  8

Subtopic:  Mass-Energy Equivalent |
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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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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:

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 |
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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) |
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The volume occupied by an atom is greater than the volume of the nucleus by factor of about

1. 1010 

2. 1015 

3. 101 

4. 105

Subtopic:  Mass-Energy Equivalent |
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A radioactive nucleus undergoes a series of decay according to the scheme 

AαA1βA2αA3γA4

If the mass number and atomic number of A are 180 and 72 respectively, then what are these number for A4?

1. 172 and 69 

2. 174 and 70

3. 176 and 69

4. 176 and 70

Subtopic:  Types of Decay |
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