BCECE Engineering BCECE Engineering Solved Paper-2009

  • question_answer
    In Rutherfords\[\alpha -\]particle experiment with thin gold foil, 8100 scintillations per minute are observed at an angle of 60°. The number of scintillations per minute at an angle of 120° will be

    A)  900                                       

    B)  2025

    C)  32400                  

    D)         4050

    Correct Answer: A

    Solution :

    Number of \[\alpha -\]particles scattered through angle \[\theta \] \[N\propto \frac{1}{{{\sin }^{4}}\left( \frac{\theta }{2} \right)}\]                 or            \[\frac{{{N}_{1}}}{{{N}_{2}}}=\frac{\left( {{\sin }^{4}}\frac{{{\theta }_{2}}}{2} \right)}{\left( {{\sin }^{4}}\frac{{{\theta }_{1}}}{2} \right)}\]                 or            \[\frac{8100}{{{N}_{2}}}=\frac{\left( {{\sin }^{4}}\frac{120}{2} \right)}{\left( {{\sin }^{4}}\frac{60}{2} \right)}\]                 or            \[\frac{8100}{{{N}_{2}}}=\frac{{{\sin }^{4}}60}{{{\sin }^{4}}30}\]                 \[\Rightarrow \]               \[{{N}_{2}}=\frac{8100\times \frac{1}{16}}{\frac{9}{16}}\]                 or            \[{{N}_{2}}=900\]


You need to login to perform this action.
You will be redirected in 3 sec spinner