During mean life of a radioactive element, the fraction that disintegrates is 
(a) e            (b)  1e
(c) e-1e     (d) ee-1

Concept Questions :-

Radioactivity
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1 Curie is equal to 
(a) 3×1010 disintegrations/sec
(b) 3.7×107 disintegrations/sec
(c) 5×107 disintegrations/sec
(d) 3.7×1010 disintegrations/sec

Concept Questions :-

Radioactivity
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The electron emitted in beta radiation originates from

(a) Inner orbits of atoms
(b) Free electrons existing in nuclei
(c) Decay of a neutron in a nucleus
(d) Photon escaping from the nucleus

Concept Questions :-

Types of decay
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When a radioactive substance emits an α-particle, its position in the periodic table is lowered by

(a) One place               (b) Two places
(c) Three places           (d) Four places

Concept Questions :-

Types of decay
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During negative β-decay 
(a) Neutron converts into proton
(b) Proton converts into neutron
(c) Neutron proton ratio increases
(d) None of these

Concept Questions :-

Types of decay
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A radioactive nucleus emits a beta particle. The parent and daughter nuclei are 
(a) Isotopes              (b) Isotones
(c) Isomers               (d) Isobars

Concept Questions :-

Types of decay
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If a radioactive substance reduces to 116 of its original mass in 40 days, what is its half-life 
(a) 10 days            (b) 20 days
(c) 40 days            (d) None of these

Concept Questions :-

Radioactivity
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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 
(a) Z – 3, N – 1                  (b) Z – 2, N – 2
(c) Z – 1, N – 3                  (d) Z, N – 4

Concept Questions :-

Radioactivity
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99% of a radioactive element will decay between

(a) 6 and 7 half lives             (b) 7 and 8 half lives
(c) 8 and 9 half lives             (d) 9 half lives

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Radioactivity
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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
(a) 4.6×1012 atoms/s          (b) 2.3×1011 atoms/s
(c) 4.6×1010 atoms/s          (d) 2.3×108 atoms/s

Concept Questions :-

Radioactivity
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