JEE Main & Advanced Physics Atomic Physics Question Bank Self Evaluation Test - Atoms

  • question_answer
    In a Rutherford experiment, the number of particles scattered at \[90{}^\circ \]angle are 28 per minute then number of scattered particles at an angle \[~60{}^\circ \] and \[120{}^\circ \] will be 

    A)               117 per minute, 25 per minute

    B)  50 per minute, 12.5 per minute

    C)  100 per minute, 200 per minute

    D)  112 per minute, 12.4 per minute

    Correct Answer: D

    Solution :

    [d] No. of particles scattered through an angle \[\theta =N\left( \theta  \right)=\frac{k{{Z}^{2}}}{{{\sin }^{4}}\left( \frac{\theta }{2} \right){{\left( K.E. \right)}^{2}}}\] \[\therefore 28=\frac{4kc{{z}^{2}}}{{{\left( K.E. \right)}^{2}}}\text{ for }\theta \text{=90}{}^\circ \] \[\therefore \frac{kc{{z}^{2}}}{{{\left( K.E. \right)}^{2}}}\text{ =}\frac{28}{4}=7\] \[\therefore N\left( 60{}^\circ  \right)=\frac{7}{{{\sin }^{4}}\left( \frac{60{}^\circ }{2} \right)}=16\times 7=112/\min .\] \[N\left( 120{}^\circ  \right)=\frac{7}{\sin \left( \frac{120{}^\circ }{2} \right)}=12.4/\min \]


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