An electron moving with a speed u along the positive x-axis at `y=0` enters a region of uniform magnetic field which exists to the right of y-axis. The electron exits from the region after some time with the speed v at coordinate y, then

Options

A. (a)`vgtu,ylt0`
B. (b)`v=u,ygt0`
C. (c)`vgtu,ygt0`
D. (d)`v=u,ylt0`

Answer

D

Explanation

Magnetic force does not change the speed of charged particle. Hence, `v=u`. Further magnetic field on the electron in the given condition is along negative y-axis in the starting. Or it describes a circular path in clockwise direction. Hence, when it exits from the field, `ylt0`