Abstract
The formation of dew and at subfreezing temperatures, frost, may occur on a solid body if proper atmospheric conditions prevail. The condensation of atmospheric moisture occurs when the temperature of the solid body is lowered by radiation of heat below the des point of the surrounding air. Because of the high surface tension of water, its condensation occurs as minute spherical droplets having distinct optical properties. Their formation on retroreflective materials, which depend on collimated incident light for efficient reflection refracts and scatters the light beam, rendering them less.