A radioactive substance has a half-life of 1 year. The fraction of this material, that would remain after 5 years will be

(1) 132             

(2) 15
(3) 12               

(4) 45

Subtopic:  Radioactivity (OLD NCERT) |
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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 

(1) 0.151 gm             

(2) 0.32 gm

(3) 1.51 gm               

(4) 0.16 gm

Subtopic:  Radioactivity (OLD NCERT) |
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Which is the correct expression for half-life

(1) t1/2=log2                 

(2) t1/2=λlog2
(3) t1/2=λlog2(2.303)     

(4) t1/2=2.303 log 2λ

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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 

1. Z – 3, A – 4           

2. Z – 1, A – 4

3. Z – 2, A – 4           

4. Z, A – 2

Subtopic:  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

(1) 0.8 curie       

(2) 0.4 curie

(3) 0.1 curie       

(4) 0.16 curie

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In a mean life of a radioactive sample 

(1) About 1/3 of substance disintegrates

(2) About 2/3 of the substance disintegrates

(3) About 90% of the substance disintegrates

(4) Almost all the substance disintegrates

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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 
(1) 12 sec           

(2) 1 sec
(3) 38 sec           

(4) 34 sec

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During mean life of a radioactive element, the fraction that disintegrates is:

(1) e           

(2)  1e
(3) e-1e     

(4) ee-1

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1 Curie is equal to 

(1) 3×1010 disintegrations/sec

(2) 3.7×107 disintegrations/sec

(3) 5×107 disintegrations/sec

(4) 3.7×1010 disintegrations/sec

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The electron emitted in beta radiation originates from

(1) Inner orbits of atoms

(2) Free electrons existing in nuclei

(3) Decay of a neutron in a nucleus

(4) Photon escaping from the nucleus

Subtopic:  Types of Decay |
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