In a radioactive substance at t = 0, the number of atoms is 8×104, its half-life period is 3 yr. The number of atoms equal to 1×104 will remain after an interval of:

1. 9 yr

2. 8 yr 

3. 6 yr 

4. 24 yr

Subtopic:  Radioactivity (OLD NCERT) |
 75%
From NCERT
PMT - 2010
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The half-life of radium is 1622 years. How long will it take for seven-eighth of a given amount of radium to decay

1. 3244 years

2. 6488 years

3. 4866 years

4. 811 years

Subtopic:  Radioactivity (OLD NCERT) |
 72%
From NCERT
PMT - 1999
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The binding energy per nucleon of deuterium and helium atom is 1.1 MeV and 7.0 MeV. If two deuterium nuclei fuse to form a helium atom, the energy released is:

1. 19.2 MeV

2. 23.6 MeV

3. 26.9 MeV 

4. 13.9 MeV

Subtopic:  Nuclear Binding Energy |
 76%
From NCERT
PMT - 2001
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The power obtained in a reactor using U235 disintegration is 1000 kW. The mass decay of \(U^{235}\) per hour is:

1. 1 microgram           

2. 10 microgram       

3. 20 microgram     

4. 40 microgram

Subtopic:  Nuclear Energy |
From NCERT
PMT - 2011
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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) |
 64%
From NCERT
PMT - 2010
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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%
From NCERT
PMT - 1997
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In the nuclear reaction: X(n, α)3Li7, the term X will be:

1. B105 

2. B95

3. B115

4. H2e4

Subtopic:  Types of Decay |
From NCERT
PMT - 2001
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10 g of radioactive material of half-life 15 year is kept in store for 20 years. The disintegrated material mass is [Pb. PMT 2002]

1. 12.5 g

2. 10.5 g

3. 6.03 g

4. 4.03 g

Subtopic:  Radioactivity (OLD NCERT) |
 57%
From NCERT
PMT - 2002
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A sample of radioactive element has a mass of 10 gm at an instant t = 0. The approximate mass of this element in the sample after two means lives in [CBSE PMT/PDT 2003]

1. 3.70 gm

2. 6.30 gm

3. 1.35 gm 

4. 2.50 gm

Subtopic:  Radioactivity (OLD NCERT) |
 50%
From NCERT
PMT - 2003
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When two deuterium nuclei fuse together to form a tritium nuclei, we get a

1. Neutron

2. Deutron

3. α-particle

4. Proton

Subtopic:  Nuclear Binding Energy |
 52%
From NCERT
PMT - 2000
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