In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life 
(a) 69.3%            (b) 63%
(c) 50%               (d) 37%

Concept Questions :-

Radioactivity
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The S.I. unit of radioactivity is 
(a) Roentgen          (b) Rutherford
(c) Curie                (d) Becqueral

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Radioactivity
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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 
(a) 60 days              (b) 30 days
(c) 40 days              (d) 240 days

Concept Questions :-

Radioactivity
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The equation XZAYZ+1A+e-10+v¯   represents- 
1. β-emission             

2. α-emission

3. e- capture             

4. Fission

Concept Questions :-

Types of decay
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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 
(a) A1t1=A2t2            (b) A1-A2=t2-t1
(c) A2=A1et1-t2/T    (d) A2=A1et1/t2T

Concept Questions :-

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

(a) YZ+2A+4                     (b) YZA
(c) YZ-2A-4                     (d) YZ-4A-2

Concept Questions :-

Types of decay
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Which of the following processes represents a gamma-decay

(a) XZA+γXZ-1A+a+b 
(b) XZA+n01XZ-2A-3+c
(c) XZAXZA+f
(d) XZA+e-1  XZ-1A+g

Concept Questions :-

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 
(a) 400 μs               (b) 6.3 μs 
(c) 40 μs                 (d) 300 μs

Concept Questions :-

Radioactivity
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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

(a) 12 h             (b) 16 h
(c) 48 h             (d) 192 h

Concept Questions :-

Radioactivity
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A radioactive substance has an average life of 5 hours. In a time of 5 hours 
(a) Half of the active nuclei decay
(b) Less than half of the active nuclei decay
(c) More than half of the active nuclei decay
(d) All active nuclei decay

Concept Questions :-

Radioactivity
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