If 20 gm of a radioactive substance due to radioactive decay reduces to 10 gm in 4 minutes, then in what time 80 gm of the same substance will reduce to 10 gm 

(1) In 8 minutes             

(2) In 12 minutes

(3) In 16 minutes             

(4) In 20 minutes

Subtopic:  Radioactivity (OLD NCERT) |
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16 gm sample of a radioactive element is taken from Bombay to Delhi in 2 hour and it was found that 1 gm of the element remained (undisintegrated). Half life of the element is 

(1) 2 hour         

(2) 1 hour

(3) 12 hour         

(4) 14hour

Subtopic:  Radioactivity (OLD NCERT) |
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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

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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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