引理1带电粒子以相同大小、不同方向的速度射入磁场,其圆心的连线为圆或圆的一部分.例1(2005年高考全国卷Ⅰ第20题)如图1,在一水平放置的平板MN的上方有匀强磁场,磁感应强度的大小为B,磁场方向垂直于纸面向里.许多质量为m带电量为+q的粒子,以相同的速率v沿位于纸面内的各个方向,由小孔O射入磁场区域.不计重力,不计粒子间的相互影响.下列图中阴影部分表示带电粒子可能经过的区域,其中.哪个图是正确的?() Lemma 1 A charged particle is injected into a magnetic field at the same size and in different directions. The centerline of the charged particle is a part of a circle or circle. Example 1 (2005 issue 20 of the national college entrance examination volume I) is shown in Figure 1, at a horizontal position. There is a uniform magnetic field above the plate MN, the magnetic induction intensity is B, and the magnetic field direction is perpendicular to the inside of the paper. Many masses are particles whose m charge is +q, at the same rate v along all directions in the paper surface. , from the small hole O into the magnetic field. Regardless of gravity, do not account for the interaction between particles. The shaded parts in the following figure indicates the areas that the charged particles may pass, where is the map correct?