The Amber Filter is a selective band-pass filter that only allows certain wavelengths of light to pass through the filter and be emitted in the searchlight’s beam. The filter blocks much of the blue light and allows the yellow light components to pass through, resulting in a beam that appears yellow or amber in color.
An amber beam of light is better for smoke or fog conditions because of the way human eyes perceive light. The wavelengths of the blocked white/blue light and passed yellow light would both penetrate the smoke/fog to a similar degree, however the issue is how the eye will perceive these colors of light as they are “backscattered” or reflected off of particles in the air. White/blue light reflected back from water and smoke particles quickly fatigues the human eye and result in the perception of glare. Yellow light, on the other hand, does not produce this effect as quickly and is thus perceived as providing better penetration.