o

No we cannot say that . See particle will strike the x-axis after one time period or it has covered distance equal to pitch. If speed and mag field both are doubled pitch remains same so particle strikes the target. But if only mag field is doubled then new pitch becomes half of initial value so particle strikes the target after covering distance =2× new pitch which is equal to old pitch.

sir,then why the second opt is correct,i mean how we know that the particle has to travel double the pitch to strike the target? sir,if the option will b=3bo,then what will happen? will the particle strikes the target?