大海为什么是蓝色的

人们常用“蔚蓝色”来形容一望无际的大海，蓝色似乎是天空和海洋的专属颜色，这是为什么呢？世界上不是还有黑海、红海吗？这又是怎么回事呢？原来，这些颜色变化都跟物理学上的“反射作用”有关系。

Sunlight is made up of all the colors of the rainbow: red, orange, yellow, green, blue, and violet. Some of the sunlight is reflected off the surface of the water, reflecting the color of the sky. Some of the sunlight penetrates¹ the water and is scattered² by ripples³ and particles in the water (this tinges⁴ the appearance of the ocean with the color of the particles). In deep water, much of the sunlight is scattered by the oxygen in the water, and this scatters⁵ more of the blue light.

Water absorbs more of the red light in sunlight; the water also enhances the scattering⁶ of blue light. Sir Chandrasekhar Venkata Raman (an Indian physicist) won the Nobel Prize in 1930 for his work on light.

Some Oddly-Colored Seas:

The Red Sea often looks red because of red algae⁷ that live in this sea.

The Black Sea looks almost black because it has a high concentration of hydrogen sulfide (which appears black).

ripple: 波纹

particle: 粒子

algae: 藻类，海藻

hydrogen sulfide: 氢硫化物