Half-life of a radioactive substance is 12.5 h and its mass is 256 g. After what time, the amount of remaining substance is 1 g? [2001]

1. 75 h

2. 100 h 

3. 125 h

4. 150 h

Subtopic:  Radioactivity (OLD NCERT) |
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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) |
 87%
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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) |
 63%
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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) |
 76%
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