NEET Sample Paper NEET Sample Test Paper-73

  • question_answer
    A nucleus of mass number A, originally at rest, emits an \[\alpha -particle\] with speed v. The daughter nucleus recoils with a speed

    A) \[\frac{2\,\nu }{A+4}\]  

    B) \[\frac{4\,\nu }{A+4}\]

    C) \[\frac{4\,\nu }{A-4}\]                

    D) \[\frac{2\,\nu }{A-4}\]

    Correct Answer: C

    Solution :

    \[\alpha -particle\] is equivalent to helium nucleus. The emission of an \[\alpha -particle\] from the atom of an element reduces its atomic number by 2 and mass number by 4. Hence, the radioactive emission is as follows \[_{Z}{{X}^{A}}{{\xrightarrow{\alpha -particle}}_{z-2}}{{X}^{A-4}}{{+}_{z}}H{{e}^{4}}\,(\alpha -Particle)\] Also from the law of conservation of momentum,   \[\operatorname{m}\,\,\times \,\,0\,\,=\,\,{{m}_{y}}{{\nu }_{y}}\,\,+\,\,{{m}_{\alpha }}{{\nu }_{\alpha }}\] \[=\left( A-4 \right){{\nu }_{y}}+4\nu \] \[\Rightarrow \,\,\,\,\,\,{{\nu }_{y}}=\frac{4\nu }{A-4}\]


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