Protons move rectilinearly in the region of space where there are uniform mutually perpendicular electric and magnetic fields `E` and `B`. The trajectory of protons lies in the plane xz as shown in the figure and forms an angle 9 with x-axis. Find the pitch of the helical trajectory along which the protons will move after the electric field is switched off.

Answer

A, B

Explanation

When they are moving recitilinearly, net force is zero.
`:. qE=Bqvsin(90^@-theta)`
`:. v=E/(Bcostheta)`
When electric field is switched off ,
`p=((2pim)/(Bq))vcos(90^@-theta)`
`=(2pim Etantheta)/(qB^2)`