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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Which of the following are suitable for the fusion process ? [2002]

(1) Light nuclei

(2) Heavy nuclei

(3) Elements lying in the middle of periodic table

(4) Elements lying in the middle of binding energy curve

Concept Questions :-

Nuclear binding energy
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An archeologist analyses the wood in a prehistoric structure and finds that C14 (Half - life=5700 years) to C12 is only one - fourth of that found in the cells buried plants. The age of the wood is about

1. 5700 yr

2. 2850 yr

3. 11,400 yr

4. 22,800 yr

 

Concept Questions :-

Radioactivity
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In the nuclear reaction: X(n, α)3Li7 the term X will be :

(1) B105                  (2) B95

(3) B115                  (4) H2e4

Concept Questions :-

Mass-energy equivalent
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10 g of radioactive material of half-life 15 year is kept in store for 20 years. The disintegrated material mass is [Pb. PMT 2002]

(1) 12.5 g               (2) 10.5 g               (3) 6.03 g              (4) 4.03 g

Concept Questions :-

Radioactivity
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If a radioactive nucleus decays according to the following reaction

X18072αX1βX2αX3γX4

then the mass number and the atomic number of X4 then the mass number and the atomic number of X4 will be, respectively [MP PET 2002]

(1) 172, 70                     (2) 172, 69

(3) 172, 68                     (4) 171, 69

Concept Questions :-

Radioactivity
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Two radioactive materials X1 and X2 have decay constants 10λ and λ respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of X1 to that of X2 will be 1e after a time

(1) 110 λ                     (2) 111 λ

(3) 1110 λ                     (4) 19 λ

Concept Questions :-

Radioactivity
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A radioactive material has mean-lives of 1620 yr and 520 yr for α and β-emission. The material decays by simultaneous α and β-emission. The time in which 1/4th of the material remains intact is 

(a) 4675 yr                                 (b) 720 yr

(c) 545 yr                                   (d) 324 yr

Concept Questions :-

Radioactivity
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