If half-life of a substance is 3.8 days and its quantity is 10.38 gm. Then substance quantity remaining left after 19 days will be 
(a) 0.151 gm             (b) 0.32 gm
(c) 1.51 gm               (d) 0.16 gm

Concept Questions :-

Radioactivity
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Which is the correct expression for half-life

(a) t1/2=log2                  (b) t1/2=λlog2
(c) t1/2=λlog2(2.303)      (d) t1/2=2.303 log 2λ

Concept Questions :-

Radioactivity
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A nucleus AZA emits an α-particle. The resultant nucleus emits a β+ particle. The respective atomic and mass no. of the final nucleus will be 
(a) Z – 3, A – 4            (b) Z – 1, A – 4
(c) Z – 2, A – 4            (d) Z, A – 2

Concept Questions :-

Types of decay
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The activity of a radioactive sample is 1.6 curie and its half-life is 2.5 days. Its activity after 10 days will be

(a) 0.8 curie       (b) 0.4 curie
(c) 0.1 curie       (d) 0.16 curie

Concept Questions :-

Radioactivity
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In a mean life of a radioactive sample 
(a) About 1/3 of substance disintegrates
(b) About 2/3 of the substance disintegrates
(c) About 90% of the substance disintegrates
(d) Almost all the substance disintegrates

Concept Questions :-

Radioactivity
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Three fourth of the active decays in a radioactive sample in 3/4 sec. The half life of the sample is 
(a) 12 sec            (b) 1 sec
(c) 38 sec            (d) 34 sec

Concept Questions :-

Radioactivity
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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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