Question

a dry road shows diffuse reflection but when wet results in specular reflection of light​

Answer 1

When a beam of light (a collection of multiple separate light rays) reflects off a rough surface, it is called diffuse reflection. Within the beam, each individual light ray approaches the surface in a parallel manner. Water can fill in the gaps and smooth down the surface if the surface is wet. When rays of light from an incoming car's headlights strike this smooth surface, they are specularly reflected and remain concentrated in a beam. This concentrated beam of reflected light causes an uncomfortable glare for the motorist hence a dry road shows diffuse reflection but when wet results in specular reflection of light​