Message 32/76
Date: 02-Nov-02 @ 08:49 PM -
RE: Ten Wacky Animal Facts
'Colour' is simply the name we give to our perception of different wavelengths/frequencies (both equivalent) of visible light. In perceiving colour, our brain only cares about the frequency of the light entering our eyes, not how it came into being.
You can have hairs that are solid, opaque and appear white just by virtue of the material they're made of, i.e. the material itself at the molecular level *reflects* most of the incident light. This is what we would call intrinsically white material. All wavelengths that fall on it are reflected back.
OR, in the polar bears' case - the hair *material* itself is optically transparent and hollow. The light is NOT reflected (at least not in the plane sense), but it passes through, being randomly scattered by the hollow hair structure. With enough of these hairs to give an equal mix of scattered components, the net result is white light. Our eyes don't care that it was scattered before arriving there.
If the polar bear's coat was materially white, a good deal of the light falling on it would be reflected away, which wouldn't help the bear keep warm. Being transparent, the light gets through to the bear's black, absorbing skin.