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📘 At first glance, white

On a bright sheet of sea ice, a polar bear can seem to dissolve into the horizon. Its colorless hairs scatter light, so the coat looks white even though it contains no white pigment.

2
lessons
~10 min
to learn
Adults
level
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What you’ll learn

  1. The coat is an optical trickExplain how pigment-free, air-filled hairs scatter light and create the appearance of a white coat.The polar bear's visible color is a structural effect produced by two layers of colorless fur.
  2. Black skin under bright furDistinguish well-supported facts about black skin and insulation from uncertain explanations about sunlight absorption.Black skin, camouflage, and insulation fit together, but the exact evolutionary purpose of the skin color remains unsettled.

Questions this course answers

Why does polar-bear fur look white if it has no white pigment?

Colorless hairs and air spaces scatter many visible wavelengths, which our eyes perceive as white.

What is true about an adult polar bear's skin?

Adult polar bears have black skin, especially evident on the nose, lips, and foot pads.

Why is the fiber-optic explanation incomplete?

The hairs are not demonstrated to function as orderly optical fibers; their structure mainly scatters light.

What can make a polar bear's coat look green in captivity?

In warm, humid conditions algae can occupy the hollow hairs and alter the light-scattering appearance.

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