【正确答案】●Ocean water is clear when there are no particles suspended in it, so light is able to pass through. ●Some water is green because of a mixture of blue light from scattered sunlight and yellow pigment from phytoplankton, the floating plant life. ●Some water is brown or brownish red because of the presence of large quantities of brown algae, which contain brown pigments. ●Some water is blue because of the scattering of sunlight by tiny particles in the water; blue light is distributed easily because it has a short wavelength.

【答案解析】[听力原文] Ocean scientists study several physical properties of water, including transparency—or water clarity—and color. Clear water indicates an absence of particles suspended in the water that would affect the ability of light to pass through it. Water clarity determines how much plant growth there may be in an ocean region. Plant growth usually depends on how deep the sunlight will reach: the clearer the water, the deeper the light will penetrate. The color of seawater varies a lot from place to place. For example, the water of the Gulf Stream in the Atlantic Ocean is a deep indigo blue, while a similar current in the Pacific off Japan is called the Black Stream because of the very dark color of its water. Along many coasts, the water is green. The green color is a mixture of blue—due to the scattering of sunlight in the water—and the soluble yellow pigment associated with phytoplankton, the floating plant life. In some places, the water is brown or brownish red. Brown or brownish red water gets its color from large quantities of certain types of microscopic brown algae. Brown algae are common along temperate coasts, where the water is cool. Their brown color comes from the brown pigments they contain. A bucket of water scooped from the surface of the sea may contain millions of microscopic brown algae. In tropical or subtropical regions, various shades of blue are common. The blue color results from the scattering of sunlight by tiny particles suspended in the water, or by molecules of the water itself. Blue light has a short wave length, and because of this, blue light is more readily distributed than light of longer wavelengths. Therefore, the ocean appears blue for the same reason that the sky does. Using points and examples from the lecture, explain why some ocean water is clear and why some water is a certain color.