An electron and a proton are moving on straight parallel paths with same velocity. They enter a semi infinite region of uniform magnetic field perpendicular to the velocity.
Which of the following statement(s) is /are true?

Options

A. Electron and proton will never come out from the magnetic field
B. Both, the electron and proton will come out of fields with their velocities parallel to each other.
C. Both particles will come out simultaneously.
D. Both particles will come out at different instants

Answer

b, d

Explanation

In such a situation, the charged particle will follow a circular path inside the field and then after completing half circle, they will come out of the magnetic field. Since both will complete their half circle inside the field, both will be moving parallel to each other. Hence option (b) is correct.
Total time taken to complete the circle also depends on mass, along with charge and magnetic field, which are same for both. Due to different masses, they will come out at different instanta. Hence option (d) is correct.