So, when reflecting off of flat water, the reflected ray becomes partially, horizontally polarized.

因此，当从平坦的水面反射时， 反射光线会变成部分水平偏振。

And if a light wave is horizontally polarized, then it won't be able to pass through the slit.

如果光波是水平偏振的， 那么它就无法通过狭缝。