十万个为什么·科学启蒙30篇（4）

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为什么海水看上去是蓝色

Pure water absorbs red, orange, and yellow light more strongly than blue light, which scatters and reflects back.
In shallow, clear seawater, this absorption-scattering effect makes the ocean look vividly blue under sunlight.
Suspended particles like plankton or silt change the color—greenish near coasts, brownish after storms.
The sky’s reflection adds brightness but isn’t the main reason; even under gray clouds, deep water stays blue.
Very deep or murky water appears dark blue or black because almost all visible light gets absorbed before returning.
Scientists measure ‘optical depth’ to predict how far down blue light travels before fading completely.
Coral reefs look turquoise because white sand reflects light upward while water absorbs longer wavelengths.
This same principle explains why glaciers and thick ice appear blue—not from impurities, but from selective absorption.

听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。

Suspended particles like plankton or silt change the color—greenish near coasts, brownish after storms. 浮游生物或泥沙等悬浮颗粒会改变海水颜色——近岸偏绿，风暴后偏褐。
In shallow, clear seawater, this absorption-scattering effect makes the ocean look vividly blue under sunlight. 在浅而清澈的海水中，这种吸收-散射效应使海洋在阳光下呈现鲜明的蓝色。
Scientists measure ‘optical depth’ to predict how far down blue light travels before fading completely. 科学家通过测量‘光学深度’来预测蓝光完全衰减前能穿透多深。

这篇中文题目最接近哪一句？为什么海水看上去是蓝色一次学校运动会的通知一份超市购物清单

课文第一句的意思更接近？纯水对红、橙、黄光的吸收强于蓝光，而蓝光则易散射并反射回来。今天学校放假了。请把窗户打开。

这一课主要在讲什么？（看英文标题） Why Seawater Appears Blue How to cook noodles A maths worksheet

Suspended particles like plankton or silt change the color—greenish near coasts, brownish after storms.

Suspended particles like plankton or silt change the color—greenish near coasts, brownish after storms.

第一版：录下来、回听、再听标准音。系统打分以后再加。

用今天的表达，自己说一句。

例子：Suspended particles like plankton or silt change the color—greenish near coasts, brownish after storms.