# When two electrons enter into a magnetic field with different velocities, they deflect in different circular paths, in such a way that the radius of one path is double that of the other $1 \times 10^7\: ms^{-1}$ is the velocity of the electron in smaller circle of radius $2 \times 10^{-3} m$ . The velocity of electron in the other circular path is :

$\begin {array} {1 1} (1)\;4 \times 10^7\: ms^{-1} & \quad (2)\;4 \times 10^6\: ms^{-1} \\ (3)\;2 \times 10^7\: ms^{-1} & \quad (4)\;2 \times 10^6\: ms^{-1} \end {array}$

(3) $2 \times 10^7\: ms^{-1}$