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Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2009

  • question_answer
    Assertion : Fission of \[_{\text{92}}^{\text{235}}\text{U}\]is brought about by a thermal neutron, whereas that of \[_{\text{92}}^{\text{238}}\text{U}\]is brought about by a fast neutron. Reason (R): \[_{\text{92}}^{\text{235}}\text{U}\]is an even-odd nucleus, whereas \[_{\text{92}}^{\text{238}}\text{U}\]is an even-even nucleus.

    A)  Both A and R are true and R is the correct explanation of A.

    B)  Both A and R are true and R is NOT a correct explanation of A.

    C)  A is true but R is false.

    D)  A is false but R is true.

    Correct Answer: B

    Solution :

    Fission of \[{{U}^{235}}\] occurs by slow neutrons only (of  energy about\[1\text{ }eV\]) or even by thermal neutrons (of energy about\[0.025\text{ }eV\]). Fission of \[_{92}^{235}U\] brought about by a fast neutrons. \[_{92}^{235}U\] has odd mass number and even atomic number, hence it is an even-odd nucleus whereas \[_{92}^{235}U\] has even mass number and even atomic number, hence is an even-even nucleus.


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