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

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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

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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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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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