Atomic mass number of an element thorium is 232 and its atomic number is 90. The end product of this radioactive element is an isotope of lead (atomic mass 208 and atomic number 82). The number of alpha and beta particles emitted is 
(a) α=3, β = 3        (b) α = 6, β = 4
(c) α=6, β=0          (d) α=4, β=6

Concept Questions :-

Types of decay
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A sample contains 16 gm of a radioactive material, the half life of which is two days. After 32 days, the amount of radioactive material left in the sample is

(a) Less than 1 mg         (b) 14gm 
(c) 12gm                       (d) 1 gm

Concept Questions :-

Radioactivity
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A radio-isotope has a half- life of 5 years. The fraction of the atoms of this material that would decay in 15 years will be

(a) 1/8              (b) 2/3
(c) 7/8              (d) 5/8

Concept Questions :-

Radioactivity
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Three α-particles and one β-particle decaying takes place in series from an isotope Ra88236. Finally the isotope obtained will be 
(a) X84220         (b) X86222
(c) X83224         (d) X83215

Concept Questions :-

Types of decay
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Half life of a radioactive substance is T. The time taken for all the nuclei to disintegrate will be
(a) 2T           (b) T2
(c) 4T           (d) Uncertain

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Radioactivity
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The half life of polonium is 140 days. After how many days, 16 gm polonium will be reduced to 1 gm (or 15g will decay) 
(a) 700 days            (b) 280 days
(c) 560 days            (d) 420 days

Concept Questions :-

Radioactivity
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A radioactive element emits 200 particles per second. After three hours 25 particles per second are emitted. The half life period of element will be
(a) 50 minutes            (b) 60 minutes
(c) 70 minutes            (d) 80 minutes

Concept Questions :-

Radioactivity
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The half life of the isotope Na1124 is 15 hrs. How much time does it take for 78th of a sample of this isotope to decay

(a) 75 hrs               (b) 65 hrs
(c) 55 hrs               (d) 45 hrs

Concept Questions :-

Radioactivity
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If the half life of a radioactive sample is 10 hours,
its mean life is 
(a) 14.4 hours               (b) 7.2 hours
(c) 20 hours                  (d) 6.93 hours

Concept Questions :-

Radioactivity
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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 
(a) In 8 minutes              (b) In 12 minutes
(c) In 16 minutes             (d) In 20 minutes

Concept Questions :-

Radioactivity
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