As you probably already know, light is a wave and has qualities similar to water waves. Imagine tossing a pebble into the still water of a pond. The impact of the pebble would create concentric waves that would radiate outward. The waves themselves consist of peaks and troughs.
If you were to place a slitted gate in the path of the radiating waves, smaller wavelets would emerge on the other side of each of the slit holes. As these wavelets emerge from the slit holes, they too would consist of peaks and troughs.
As these wavelets radiate into each other, the wavelet peaks will cancel the troughs of adjacent wavelets. If it is a perfect collision of equal magnitude, the waves would disappear completely. However, it is not a perfect collision and the intensity of the wave is only reduced. The result is what is called a "wave interference pattern."
If you were to throw a handful of pebbles into the same pond, you would have a momentary disturbance; but, the peaks and troughs will quickly cancel each other and the disturbance will settle quickly.
Our no-see-um mesh has 800 holes per square inch. And two factors reduce the intensity of light. The first is that the threads themselves physically block some of the light. In addition, the interference pattern reduces the intensity of the light that passes through. In fact we sell to the film industry who makes giant outdoor "butterfly screen" light filters for outdoor scenes and to the military for urban camouflage.
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