🌈 光的色散：白光里藏着彩虹🌈 Light Dispersion: A Rainbow Hiding in White Light
上一片里，透镜把光掰弯、聚成清晰的像。这一片再进一步：看起来没颜色的白光，身体里藏着一整条彩虹。Last leaf, a lens bent light into a clear image. This leaf goes one step further: plain white light is hiding a whole rainbow.
第 1 步：三棱镜把白光摊开Step 1: A prism fans white light out
小火箭实验室的经典一幕：一束白光射进三棱镜。A classic scene in Rocket's lab: one white beam enters a prism.
白光其实是七种颜色混在一起。进玻璃后，每种颜色的折射率不同：紫光偏折最大、红光最小，于是走散成红橙黄绿蓝靛紫的彩带——这就是色散。不是玻璃染了色，是偏折不一样。White light is seven colours mixed together. In glass each colour has its own refractive index: violet bends most, red least, so they fan out into a red-to-violet band — that's dispersion. No dye involved, just different bending.
那雨后的彩虹，是不是天上挂了个大棱镜？So is a rainbow a giant prism hanging in the sky?
第 2 步：彩虹是小水滴的杰作Step 2: A rainbow is tiny raindrops' work
差不多！阳光射进空中的小水滴，在水滴里折射、反射、再折射，两次折射把颜色摊开。红光出射约 42°、紫光约 40°，所以彩虹总是红在外、紫在内。想看到它，太阳得在你身后。Almost! Sunlight enters a raindrop, reflects off its back, then refracts out — bent twice, the colours spread. Red exits at about 42°, violet at about 40°, so a rainbow is always red outside, violet inside. The sun must be behind you.
光能拆开，能不能像调颜料一样调出来？Light splits apart — can it also be mixed like paint?
第 3 步：光的三原色Step 3: The three primary colours of light
能，但规则不一样。光的三原色是红、绿、蓝：三盏全开叠成白光，两两相叠得到黄、青、品红。物体颜色其实是它反射的光：红旗反射红光、吸掉其余，白纸反射所有色光，煤块几乎全吸掉。Yes, with different rules. The primary colours of light are red, green and blue: all three together make white, and pairs make yellow, cyan and magenta. An object's colour is the light it reflects: a red flag reflects red and swallows the rest, white paper bounces everything back, coal absorbs almost all.
🎮 你来当光学家（1 分钟）🎮 Your turn: be the light scientist (1 minute)
道理讲完了。先拖入射角看七色怎么分开，再完成 4 关调色：把红绿蓝三盏灯调到目标色。Theory done. First drag the angle to split the seven colours, then clear 4 mixing levels: switch the red, green and blue lamps to match each target colour.
一句话记住它：白光 = 七彩混合；三棱镜和小水滴靠「不同颜色偏折不同」把它摊开；光的三原色是红、绿、蓝。Remember it in one line: white light is seven colours mixed; a prism or a raindrop spreads them because each colour bends differently; light's primary colours are red, green and blue.
色散：紫光偏折最大、红光最小，七色散开Dispersion: violet bends most, red least — the colours fan out彩虹：阳光在水滴里折射—反射—折射，红在外紫在内Rainbow: sunlight refracts–reflects–refracts in raindrops, red outside violet inside物体颜色 = 它反射的光；光的三原色是红绿蓝An object's colour is the light it reflects; light's primaries are red, green, blue
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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