Unit of radioactivity is Rutherford. Its value is

(1) 3.7×1010 disintegrations/sec

(2) 3.7×106 disintegrations/sec

(3) 1.0×1010disintegrations/sec

(4) 1.0×106 disintegrations/sec

Subtopic:  Radioactivity (OLD NCERT) |
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A radioactive substance has a half life of 60 minutes. After 3 hours, the fraction of atom that have decayed would be

(1) 12.5%               

(2) 87.5%

(3) 8.5%                 

(4) 25.1%

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An element used for radioactive carbon dating for more than 5600 years is 

(1) C-14         

(2) U-234

(3) U-238       

(4) Po-94

Subtopic:  Radioactivity (OLD NCERT) |
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N atoms of a radioactive element emit n alpha particles per second. The half life of the element is

(1) nN sec                   

(2) Nn sec

(3) 0.693 Nn sec           

(4)  0.693 nN sec

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The radioactive nucleus N713 decays to C613 through the emission of 

(1) Neutron             

(2) Proton

(3) Electron             

(4) Positron

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The radioactive decay of uranium into thorium is expressed by the equation U92238Th90234+X where 'X' is

(1) An electron               

(2) A proton

(3) A deuteron                 

(4) An alpha particle

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In a radioactive decay, neither the atomic number nor the mass number changes. Which of the following would be emitted in the decay process 

(1) Proton             

(2) Neutron

(3) Electron           

(4) Photon

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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%

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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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