Dry hair reflects back some of the light to our eyes and some of the light is absorbed by the pigment in the hair. Water affects the way light gets bounced off our hair to our eyes. When our hair is wet, it not only sticks or joins the individual hair together but also forms a thin film on our hair. This, in turn, affects the way light bounces off our wet hair. The wet hair tends to trap or absorb the light and less light is reflected back to our eyes. The result is that it appears darker.
