Haryana PMT Haryana PMT Solved Paper-1999

  • question_answer
    A charged particle moving in a uniform magnetic field penetrates a layer of lead and thereby losses one half of its kinetic energy. The radius of curvature of its path becomes :

    A) \[\frac{1}{\sqrt{2}}\]                                     

    B) \[\sqrt{2}\]

    C) \[\frac{3}{\sqrt{2}}\]                                     

    D) \[\frac{2}{\sqrt{3}}\]

    Correct Answer: A

    Solution :

                    The radius of circular path is given by \[r=\frac{\mu \upsilon }{qB}\] If \[{{E}_{K}}\]be kinetic energy of particle then its momentum                 \[p=m\upsilon =\sqrt{2m{{E}_{K}}}\] So, the radius is given by                 \[r=\sqrt{\frac{2m{{E}_{K}}}{qB}}\] So,          \[r\propto \sqrt{{{E}_{K}}}\] Therefore, when kinetic energy is halved the radius is reduced to \[\frac{1}{\sqrt{2}}\] times its initial value.


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