Two charged particles of mass $m$ and charge $q$ each are projected from origin simultaneously with same speed $V$ in transverse magnetic field. If ${\vec r_1}$ and ${\vec r_2}$ are the position vectors of particles (with respect to origin) at $t = \frac{{\pi m}}{{qB}}$ then the value of  ${\vec r_1}.{\vec r_2}$ at that time is

821-378

  • A

    ${\left( {\frac{{mv}}{{qB}}} \right)^2}$

  • B

    $\frac{1}{2}{\left( {\frac{{mv}}{{qB}}} \right)^2}$

  • C

    $2{\left( {\frac{{mv}}{{qB}}} \right)^2}$

  • D

    $4{\left( {\frac{{mv}}{{qB}}} \right)^2}$

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