The half life period of a radioactive substance is 5 min. The amount of substance decayed in 20 min will be

(1) 93.75%                 

(2) 75%

(3) 25%                       

(4) 6.25%

Subtopic:  Radioactivity (OLD NCERT) |
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In the uranium radioactive series, the initial nucleus is U92238 and the final nucleus is Pb82206. When the uranium nucleus decays to lead, the number of  α-particles emitted will be 

(1) 1               

(2) 2

(3) 4               

(4) 8

Subtopic:  Types of Decay |
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Which of the following is a correct statement

(1) Beta rays are same as cathode rays

(2) Gamma rays are high energy neutrons

(3) Alpha particles are singly ionized helium atoms

(4) Protons and neutrons have exactly the same mass

Subtopic:  Types of Decay |
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The half life of I131 is 8 days. Given a sample of I131 at time t = 0, we can assert that 
(1) No nucleus will decay before t = 4 days

(2) No nucleus will decay before t = 8 days

(3) All nuclei will decay before t = 16 days

(4) A given nucleus may decay at any time after t = 0

Subtopic:  Radioactivity (OLD NCERT) |
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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 |
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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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