Carbon-14 decays with half-life of about 5,800 years. In a sample of bone, the ratio of carbon-14 to carbon-12 is found to be 14 of what it is in free air. This bone may belong to a period about x centuries ago, where x is nearest to 

(1) 2×58                       

(2) 58

(3) 58/2                         

(4) 3×58

Subtopic:  Radioactivity (OLD NCERT) |
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In the disintegration series U92238αXβ-YZA the values of Z and A respectively will be 

(1) 92, 236               

(2) 88, 230

(3) 90, 234               

(4) 91, 234

Subtopic:  Radioactivity (OLD NCERT) |
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The particles emitted by radioactive decay are deflected by magnetic field. The particles will be

(1) Protons and α-particles

(2) Electrons, protons and α-particles

(3) Electrons, protons and neutrons

(4) Electrons and α-particles

Subtopic:  Types of Decay |
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Half life of a radioactive element is 10 days. The time during which quantity remains 1/10 of initial mass will be

(1) 100 days             

(2) 50 days

(3) 33 days               

(4) 16 days

Subtopic:  Radioactivity (OLD NCERT) |
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In the given nuclear reaction A, B, C, D, E represents
U92238αThBAβPaDCEU92234

(1) A = 234, B = 90, C = 234, D = 91, E = β

(2) A = 234, B = 90, C = 238, D = 94, E =α

(3) A = 238, B = 93, C = 234, D = 91, E = β

(4) A = 234, B = 90, C = 234, D = 93, E = α

Subtopic:  Types of Decay |
 87%
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If half life of a radioactive element is 3 hours, after 9 hours its activity becomes 

(1) 1/9                     

(2) 1/27

(3) 1/6                     

(4) 1/8

Subtopic:  Radioactivity (OLD NCERT) |
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At any instant the ratio of the amount of radioactive substances is 2 : 1. If their half lives be respectively 12 and 16 hours, then after two days, what will be the ratio of the substances?

(1) 1 : 1                 

(2) 2 : 1

(3) 1 : 2                 

(4) 1 : 4

Subtopic:  Radioactivity (OLD NCERT) |
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Which of the following isotopes is used for the treatment of cancer 

(1) K40        

(2) Co60

(3) Sr90       

(4) I131

Subtopic:  Radioactivity (OLD NCERT) |
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If half-life of a radioactive atom is 2.3 days, then its decay constant would be 

(1) 0.1           

(2) 0.2

(3) 0.3           

(4) 2.3

Subtopic:  Radioactivity (OLD NCERT) |
 81%
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A radio isotope has a half life of 75 years. The fraction of the atoms of this material that would decay in 150 years will be

(1) 66.6%               

(2) 85.5%

(3) 62.5%               

(4) 75%

Subtopic:  Radioactivity (OLD NCERT) |
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