彩虹为什么总是七种颜色?雨后天空的哪里最容易看到它?
Why does a rainbow show seven colors — where should I look after rain?
彩虹是阳光在小雨滴里的两段旅程:先折射进入水滴,在内壁反射一次,再折射出来。不同颜色的光折射角度不同,白光被拆成红橙黄绿蓝靛紫的扇形,永远出现在背对太阳、约42度的方向上。雨刚停、太阳露脸时最容易看到;有时还能看到第二道颜色顺序相反的霓。
A rainbow is sunlight playing two journeys inside raindrops: refracting in, reflecting once off the back wall, refracting out. Each color bends differently, fanning white light into red through violet at a constant forty-two degrees from the antisolar point — so look with your back to the sun as rain ends. A fainter second bow sometimes reverses the colors.
难度 进阶 · 适合 小学高段(9-12)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#彩虹 #折射 #色散
为什么我的影子一直跟着我?它是另一个小朋友吗?
Why does my shadow copy me — is it another kid?
影子不是小朋友,是你挡住光留下的一片黑黑的地方。你举手它也举手,你跳它也跳,因为它就是你身体的轮廓呀。晚上灯一关,光不见了,影子也就回家睡觉了。
Your shadow is not a friend — it is the dark spot where your body blocks light. Raise a hand, it raises one; jump, it jumps too, because it is your own outline. Lights out means no light, and the shadow goes to sleep.
难度 入门 · 适合 幼儿(3-6)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 2 条独立证据
来源 · Source
《十万个为什么》第六版物理分册,少年儿童出版社,2013
Ten Thousand Whys: Physics volume, 6th ed., Juvenile and Children Publishing House, 2013
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-7-5324-9328-9 · 核验依据 2 ISBN 9787532493289
#影子 #光 #游戏
一天当中,影子为什么会一会儿长、一会儿短?
Why does your shadow change from long to short during the day?
太阳在天上的位置一天里不停变化。早上太阳低低的,影子被拉得长长的;中午太阳升到最高,影子缩得最短;傍晚太阳又变低了,影子重新变长。身体挡住光,光走直线绕不过去,地上就有了影子,这叫光的直线传播。
The sun keeps moving across the sky all day. In the morning it sits low, so your shadow stretches out long. At noon the sun climbs highest, so the shadow shrinks shortest. In the evening the sun sinks low again and the shadow grows long once more. Your body blocks sunlight, and light travels in straight lines, so this dark shape appears on the ground.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 2 条独立证据
来源 · Source
《十万个为什么》第六版物理分册,少年儿童出版社,2013
Ten Thousand Whys: Physics volume, 6th ed., Juvenile and Children Publishing House, 2013
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-7-5324-9328-9 · 核验依据 2 ISBN 9787532493289
#影子 #光的直线传播 #太阳位置