1. How many electrons are contained in ^238₉₂U nucleus ?

(A) 92
(B) 146
(C) 238
(D) O

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2. Chadwick was awarded the Nobel prize in Physics in 1935 for his discovery of :

(A) electron
(B) proton
(C) neutron
(D) None of these

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3. The density of a nucleus is of the order of:

(A) 1015 kg m^-3
(B) 1018 kg m^-3
(C) 1017 kg m^-3
(D) 1016 kg m^-3

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4. In the given reaction :

radioactive radiations are emitted in the sequence

(A) ∝, β, ϒ
(B) β, ∝, ϒ
(C) ϒ, ∝, β
(D) β, ϒ, ∝

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5. When the mass of a sample of a radioactive substance decreases, the mean life of the sample :

(A) increases
(B) decreases
(C) remain unchanged
(D) first decreases then increases

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6. The order of nuclear density is :

(A) 10³
(B) 10¹⁷
(C) 10⁶
(D) None

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7. The isotope generally used for the treatment of cancer is :

(A) I¹³¹
(B) Hg¹⁹⁷
(C) O¹⁵
(D) Co⁶⁰

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8. What percentage of radioactive substance is left after 5 half lives ?

(A) 3.125 %
(B) 6.25 %
(C) 12.33 %
(D) 31 %

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9. Mass is converted into energy according to the relation:

(A) E = me2
(B) E = mgh
(C) E = 1/2me²
(D) E = mgH/C²

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10. The helium atom does not contain :

(A) two protons
(B) two electrons
(C) two neutrons
(D) six nucleons

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11. The more readily fissionable isotope of uranium has an atomic mass of :

(A) 234
(B) 235
(C) 236
(D) 238

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12. Energy of electron in the 1st orbit of H-atom is :

(A) -13.6 MeV
(B) –13.6 eV
(C) –13.6 J
(D) 13.6 J

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13. The mass no. of a nucleus is M and its atomic no. is z. The number of neutrons in the nucleus is :

(A) M – Z
(B) M
(C) Z
(D) M + Z

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14. The phenomena of radioactivity is :

(A) Exothermic change with increase or decrease with temperature
(B) increases on applied pressure
(C) nuclear process does not depend on external factors
(D) None of these

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15. What percentage of original radioactive atom is left after four half life ?

(A) 6%
(B) 10%
(C) 20%
(D) 25%