Multiple scattering
Here an electron undergoes more than 20 scattering events as it passes through a specimen. This would only occur on rare occasions, e.g. with very thick or dense specimens.
入射电子射向物质时，会多次受到物质中多个电子或原子核的散射（即多次散射），从而使得入射电子在遭到多次碰撞以后，其在各个方向上的散射概率趋于一致。由于散射截面与原子序数的平方成正比，因而对于轻元素，其散射的概率要小于重元素。