Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2008

  • question_answer
      An alpha nucleus of energy \[\frac{1}{2}m{{v}^{2}}\] bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to

    A)  v2                                          

    B)  1 /m

    C)  1/v4                                      

    D)  1/Ze

    Correct Answer: B

    Solution :

    Since, here nuclear target is heavy it can be assumed safely that it will remain stationary and will not move due to the Coulombic interaction force. At distance of closest approach relative velocity of two particles is v. Here target is considered as stationary, so a-particle comes to res-instantaneously  at  distance   of  closes- approach. Let required distance is r. then from:                                 \[0-\frac{m{{v}^{2}}}{2}=-\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{Ze\times 2e}{r}\]                 \[\Rightarrow \]               \[r\propto \frac{1}{m}\]                                 \[\propto \frac{1}{{{v}^{2}}}\]                                 \[\propto Z{{e}^{2}}\]


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