題組內容

7. As shown in the figure, there is a homogeneous magnetic field pointing to the positive z direction in the region x>0. An electron enters the magnetic field at point O with a velocity pointing along the tx direction. 0.63 microseconds later, it arrives at point A. 65a8734c98aa7.jpg#s-188,265

(a) What is the direction of the electron's velocity when it reaches A? Provide quantitative arguments for your answer. (5%)