fatllama
A dye laser (3)
View along the exit direction. You can actually see the laser beam for two reasons: dust and Rayleigh scattering. The beam inside of the laser cavity is perhaps 100 or more times as intense as the beam upon exit: it actually forms a weak dipole force trap for dust particles in the air which sparkle. In addition to the glowing dust, Rayleigh scattering off of air molecules is observed: because the beam is polarized vertically, it is more visible when viewed from the side than when viewed from the top.
A dye laser (3)
View along the exit direction. You can actually see the laser beam for two reasons: dust and Rayleigh scattering. The beam inside of the laser cavity is perhaps 100 or more times as intense as the beam upon exit: it actually forms a weak dipole force trap for dust particles in the air which sparkle. In addition to the glowing dust, Rayleigh scattering off of air molecules is observed: because the beam is polarized vertically, it is more visible when viewed from the side than when viewed from the top.