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

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Radioactivity
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The radioactivity of an element becomes 164th of its original value in 60 seconds. Then the half value period is

(1) 5 sec              (2) 10 sec            (3) 20 sec            (4) 30 sec

Concept Questions :-

Radioactivity
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A nucleus of P84210o originally at rest emits α particle with speed ν. What will be the recoil speed of the daughter necleus. [DCE 2002]

(1) 4ν / 206                          (2) 4ν / 214

(3) ν / 206                            (4) ν / 214

Concept Questions :-

Types of decay
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An atom of mass number 15 and atomic number 7 captures an α-particle and then emits a proton. The mass number and atomic number of the resulting product will respectively be

(1) 14 and 2                          (2) 15 and 3

(3) 16 and 4                          (4) 18 and 8

Concept Questions :-

Types of decay
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If radius of the Al1327 nucleus is estimated to be 3.6 fermi then the radius of T52125e nucleus be nearly

(a) 4 Fermi                                     (b) 5 Fermi

(c) 6 Fermi                                     (d) 8 Fermi

Concept Questions :-

Mass-energy equivalent
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Solar energy is mainly caused due to [2003]

(1) fusion of protons during synthesis of heavier elements

(2) gravitational contraction

(3) burning of hydrogen in the oxygen

(4) fission of uranium present in the sun

Concept Questions :-

Mass-energy equivalent
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A sample of radioactive elements contains 4×1010 active nuclei. If half-life of element is 10 days, then the number of decayed nuclei after 30 days is [2002]

(1) 0.5×1010                   (2) 2×1010

(3) 3.5×1010                   (4) 1×1010

Concept Questions :-

Radioactivity
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A and B are two radioactive substances whose half-lives are 1 and 2 years respectively. Initially 10 g of A and 1 g of B is taken. The time (approximate) after which they will have the same quantity remaining is

(1) 6.62 yr                (2) 5 yr                (3) 3.2 yr                   (4) 7 yr

Concept Questions :-

Radioactivity
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In radioactive decay process, the negatively charged emitted β-particles are 

(a) the electrons present inside the nucleus

(b) the electrons produced as a result of the decay of neutrons inside the nucleus 

(c) the electrons produced as a result of collisions between atoms

(d) the electrons orbiting around the nucleus

Concept Questions :-

Radioactivity
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