A nucleus with mass number 220 initially at rest emits an α-particle. If the Q value of the reaction is 5.5 MeV, calculate the kinetic energy of the α-particle

(1) 4.4 MeV             

(2) 5.4 MeV

(3) 5.6 MeV             

(4) 6.5 MeV

Subtopic:  Types of Decay |
 70%
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The half life of radioactive Radon is 3.8 days. The time at the end of which 1/20 th of the Radon sample will remain undecayed is
(Given log10e=0.4343
(a) 3.8 days               (b) 16.5 days
(c) 33 days                (d) 76 days

Subtopic:  Radioactivity (OLD NCERT) |
 78%
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If 10% of a radioactive material decays in 5 days, then the amount of original material left after 20 days is approximately
(1) 60%             

(2) 65%

(3) 70%             

(4) 75%

Subtopic:  Radioactivity (OLD NCERT) |
 62%
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A radioactive isotope X with a half-life of 1.37×109 years decays to Y which is stable. A sample of rock from the moon was found to contain both the elements X and Y which were in the ratio of 1 : 7. The age of the rock is
(a) 1.96×108 years         (b) 3.85×109 years
(c) 4.11×109years          (d) 9.59×109 years

Subtopic:  Radioactivity (OLD NCERT) |
 75%
From NCERT
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From a newly formed radioactive substance (Half-life 2 hours), the intensity of radiation is 64 times the permissible safe level. The minimum time after which work can be done safely from this source is:
1. 6 hours           
2. 12 hours
3. 24 hours         
4. 128 hours

Subtopic:  Radioactivity (OLD NCERT) |
 82%
From NCERT
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The half-life of radium is 1620 years and its atomic weight is 226 kg per kilo mol. The number of atoms that will decay from its 1 gm sample per second will be:

(1) 3.61×1010    

(2) 3.6×1012

(3) 3.11×1015     

(4) 31.1×1015

(Avogardo's number N = 6.02×1026 atoms/mol)

Subtopic:  Radioactivity (OLD NCERT) |
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A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years. The time (in years) after which one- fourth of the material remains is 
(a) 1080         (b) 2430
(c) 3240         (d) 4860

Subtopic:  Radioactivity (OLD NCERT) |
 51%
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The half life period of a radioactive element X is same as the mean life time of another radioactive element Y. Initially both of them have the same number of atoms. Then

(1) X and Y have the same decay rate initially

(2) X and Y decay at the same rate always

(3) Y will decay at a faster rate than X

(4) X will decay at a faster rate than Y

Subtopic:  Radioactivity (OLD NCERT) |
 59%
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For a substance, the average life for α-emission is 1620 years and for β emission is 405 years. After how much time the 1/4 of the material remains after simultaneous emission:

1. 1500 years            2. 300 years
3. 449 years              4. 810 years

Subtopic:  Types of Decay |
 57%
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A radioactive nucleus undergoes α-emission to form a stable element. What will be the recoil velocity of the daughter nucleus if v is the velocity of α-particle and A is the atomic mass of radioactive nucleus ?


1. 4VA-4             2. 2VA-4
3. 4VA+4             4. 2VA+4

Subtopic:  Types of Decay |
 74%
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