1 Curie is equal to 

(1) 3×1010 disintegrations/sec

(2) 3.7×107 disintegrations/sec

(3) 5×107 disintegrations/sec

(4) 3.7×1010 disintegrations/sec

Subtopic:  Radioactivity (OLD NCERT) |
 62%
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The electron emitted in beta radiation originates from

(1) Inner orbits of atoms

(2) Free electrons existing in nuclei

(3) Decay of a neutron in a nucleus

(4) Photon escaping from the nucleus

Subtopic:  Types of Decay |
 81%
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When a radioactive substance emits an α-particle, its position in the periodic table is lowered by

(1) One place             

(2) Two places

(3) Three places           

(4) Four places

Subtopic:  Types of Decay |
 85%
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A radioactive nucleus emits a beta particle. The parent and daughter nuclei are 

(1) Isotopes             

(2) Isotones

(3) Isomers               

(4) Isobars

Subtopic:  Types of Decay |
 70%
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If a radioactive substance reduces to 116 of its original mass in 40 days, what is its half-life 

(1) 10 days           

(2) 20 days

(3) 40 days           

(4) None of these

Subtopic:  Radioactivity (OLD NCERT) |
 84%
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A radioactive nucleus with Z protons and N neutrons emits an α-particle, 2β-particles and 2 gamma rays. The number of protons and neutrons in the nucleus left after the decay respectively, are 

(1) Z – 3, N – 1                 

(2) Z – 2, N – 2

(3) Z – 1, N – 3                 

(4) Z, N – 4

Subtopic:  Radioactivity (OLD NCERT) |
 73%
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99% of a radioactive element will decay between

(1) 6 and 7 half lives             

(2) 7 and 8 half lives

(3) 8 and 9 half lives             

(4) 9 half lives

Subtopic:  Radioactivity (OLD NCERT) |
 56%
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The half-life of a radioactive substance against α-decay is 1.2×107 s. What is the decay rate for 4×1015 atoms of the substance

(1) 4.6×1012 atoms/s         

(2) 2.3×1011 atoms/s

(3) 4.6×1010 atoms/s          

(4) 2.3×108 atoms/s

Subtopic:  Radioactivity (OLD NCERT) |
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In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life 

(1) 69.3%           

(2) 63%

(3) 50%               

(4) 37%

Subtopic:  Radioactivity (OLD NCERT) |
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The S.I. unit of radioactivity is 

(1) Roentgen         

(2) Rutherford

(3) Curie               

(4) Becqueral

Subtopic:  Radioactivity (OLD NCERT) |
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