light and particles in water I'm an architecture student with a very basic knowledge of phyics! My project involves shining a beam of light through water that contains particles (in this case salt). What I want to know is why the brightness of the illuminated particles changes when you look at it from different angles i.e. the beam almost disappears when you stand perpendicular to it and the intensity increases as you walk through a 90 degree angle to stand parallel to the beams of light (caught in the headlights!). Obviously, when you stand facing the beam of light its at its brightest, but why is is it that you don't see the reflection of light off the salt when standing perpendicular to the beam direction?