THE EFFECT OF SURFACE FOG ON THE TRANSMITTANCE OF LIGHT

It is shown theoretically that surface fog can reduce the transmittance of normally incident light through transparent materials from about 90% to nearly 50%. This result is also confirmed experimentally by reflectance measurements. The most important parameter is the contact angle which the droplets make with the surface. For contact angles less than about 40-degrees, there is almost no loss in transmission. For larger contact angles, there is a significant decrease in the transmittance, with the worst case occurring for a contact angle of 90-degrees.