- 1 decade agoFavorite Answer
I'll assume you have a beam that you want to track. There are two ways to do this. If the beam is of a visible wavelength, all you have to do is introduce something to scatter the beam. Favorites include fogs and smoke, although if your environment is dusty enough your scattering material is all around you.
For wavelengths outside the visible spectrum, you'll generally trace the beam with a piece of something the will fluoresce when excited by that wavelength. If your laser is an IR laser, you should also be able to view the beam with night vision goggles.