Velocity selector. Consider a charged particle moving through a region in which the elec...

Velocity selector. Consider a charged particle moving through a region in which the electric field is perpendicular to the magnetic field, with both fields perpendicular to the initial velocity of the particle (Fig. P20.62). Such a device is called a velocity selector because for one particular value of the particle speed the particle will travel straight through the device without being deflected, whereas particles with speeds that are either less than or greater than will be deflected. Consider a case with E = 500 V/m and B = 0.25 T. (a) When protons are used, what speed is selected? (b) What is the speed selected for ions? (c) If you were to use your selector with what change would be necessary?