What fraction of a radioactive material will get disintegrated in a period of two half-lives. 

 

(1) whole                (2) half                (3) one-fourth                (4) three-fourth

Concept Questions :-

Radioactivity
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If the nucleus A1327l has a nuclear radius of about 3.6 fm, then T52125e would have its radius approximately as [2007]

(1) 6.0 fm                   (2) 9.6 fm                 (3) 12.0 fm                   (4) 4.8 fm

Concept Questions :-

Mass-energy equivalent
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After two hours, one-sixteenth of the starting amount of a certain radioactive isotope remained undecayed. The half life of the isotope is [Bihar MEE 1995; Manipal MEE 1995; MP PMT 1997; AFMC 2000, 05; DPMT 2002]

(1) 15 minutes                   (2) 30 minutes

(3) 45 minutes                   (4) 1 hour

Concept Questions :-

Radioactivity
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Atomic weight of boron is 10.81 and it has two isotopes B510 and B511. Then, the ratio of atoms of  B510 and B511 in nature would be 

(1) 19 : 81                   (2) 10 : 11                (3) 15 : 16                 (4) 81 : 19

Concept Questions :-

Mass-energy equivalent
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The half-life of radium is 1600 yr.  The fraction of a sample of radium that would remain

after 6400 yr [1991]

(1) 14                (2) 12                 (3) 18                   (4) 116

Concept Questions :-

Radioactivity
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The count rate of a Geiger Muller counter for the radiation of a radioactive material of half-life 30 min decreases to 5 s-1 after 2 h. The initial count rate was [1995]

(1) 20 s-1             (2) 25 s-1             (3) 80 s-1              (4) 625 s-1

Concept Questions :-

Radioactivity
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An element A decays into element C by a two step process

AB+H2e4BC+2e-

then  [1989]

(1) A and C are isotopes

(2) A and C are isobars

(3) A and B are isotopes

(4) A and B are isobars

Concept Questions :-

Types of decay
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The radius R of a nuclear matter varies with A as

(1) R α A2/3                         (2) R α A1/3

(3) R α A0                             (4) R α A

Concept Questions :-

Mass-energy equivalent
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Number of nuclei of a radioactive substance at time t = 0 are 2000 and 1800 at time t = 2s. Number of nuclei left after t = 6s is [MGIMS 2010]

(1) 1442               (2) 1554                 (3) 1652                 (4) 1458

Concept Questions :-

Radioactivity
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In a radioactive material the activity at time t1 is R1 and at a later time t2, it is R2. If the decay constant of the material is λ, then

(a) R1=R2e-λt1-t2                                    (b) R1=R2eλt1-t2

(c) R1=R2t2t1                                          (d) R1=R2

Concept Questions :-

Radioactivity
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