Tuesday, July 8, 2014

Why do we see dust particles in bright narrow beam of light?


The particles are always present in air. Normally, they reflect less light, because the particles are very small. They can only be seen when a strong beam of light passes through the air. This is called Tyndall Effect. A very strong concentrated light beam reflects off of the dust in the air which can be seen in a darkened room, which is normally not seen.
Our eyes become more sensitive to light in dark rooms, especially if we give them a few minutes to adjust. Also the illuminated dust in a beam of light shows up because of the contrast between it and the dark background when the room is dark.