Laser beam attenuation by scattering. In this photograph a diode laser beam (635 nm) propagates through a cuvette filled with water with few drops of milk added. Milk contains tiny globules of fat which scatter light from the beam. Light scattering by small particles (about the size of wavelength) in a colloid or suspension is called Tyndall effect. Because scattering removes light from the beam, it is attenuated along the direction it propagates. Exponential attenuation of light is known as the Beer-Lambert-Bouguer law.