First off, let me apologize if this is in the wrong section, but I was not entirely sure what branch the answer would fall under. Okay, my question is this (and its probably pretty obvious): If water is clear, what makes it an almost perfect mirror when you look across a still lake? My thoughts were perhaps the substances in the water affecting the change, or perhaps surface tension and light played a roll...but I'm really just stabbing in the dark here. Any help wpuld be greatly appreciated. Thank you in advance.