易混淆的单词： Schlieren

They used what is known as schlieren photography to catch the shock wave .

他们使用了一种被称为纹影摄影的技术来捕捉冲击波。

Because shock waves represent a stark and sudden change in refractive index , they show up clearly in schlieren photographs .

因为冲击波反映了折射率的明显和突然的变化，他们能在纹影摄影中清楚地被展现出来。