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%

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The S.I. unit of radioactivity is 

(1) Roentgen         

(2) Rutherford

(3) Curie               

(4) Becqueral

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A radioactive material has an initial amount 16 gm. After 120 days it reduces to 1 gm, then the half-life of radioactive material is 

(1) 60 days             

(2) 30 days

(3) 40 days             

(4) 240 days

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The activity of a sample of a radioactive material is A1, at time t1 and A2 at time t2 (t2>t1). If its mean life T, then 

(1) A1t1=A2t2           

(2) A1-A2=t2-t1
(3) A2=A1et1-t2/T   

(4) A2=A1et1/t2T

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Nucleus produced due to α-decay of the nucleus XZA is

(1) YZ+2A+4                     

(2) YZA

(3) YZ-2A-4                    

(4) YZ-4A-2

Subtopic:  Types of Decay |
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Which of the following processes represents a gamma-decay

(1) XZA+γXZ-1A+a+b 

(2) XZA+n01XZ-2A-3+c

(3) XZAXZA+f

(4) XZA+e-1  XZ-1A+g

Subtopic:  Types of Decay |
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The half-life of At215 is 100 μs. The time taken for the radioactivity of a sample of At215 to decay to 1/16th of its initial value is 

(1) 400 μs               

(2) 6.3 μs 

(3) 40 μs                 

(4) 300 μs

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The half-life of a radioactive substance is 48 hours. How much time will it take to disintegrate to its 116th part

(1) 12 h             

(2) 16 h

(3) 48 h             

(4) 192 h

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A radioactive substance has an average life of 5 hours. In a time of 5 hours 

(1) Half of the active nuclei decay

(2) Less than half of the active nuclei decay

(3) More than half of the active nuclei decay

(4) All active nuclei decay

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