Somewhere over the Double Rainbow 飞越双彩虹

What happens when you cross sunshine and rain? You have rainbow of course! Sometimes, if you are lucky, you might see two rainbows, like these pictures here! Isn't it interesting that the second, weaker rainbow has a reversed colour scheme? That's because it is essentially a reflection of the original rainbow by the rain drops!

阳光和雨水加起来是什么？当然是彩虹啦！有时候，运气好的话还可以看见双彩虹呢！看见了吗？那第二道彩虹的颜色是反的！这是因为第二道彩虹其实是原彩虹的倒影。

Rainbows form from the refraction of sunlight by raindrops. Sunlight is in fact a mixture of different colour lights. Each colour light have a different wavelength, and have a different refractive index in water. This that these light will be refracted at different angles. Blue light has the shortest wavelength, hence a larger refractive index and larger refracted angle. Red light has the longest wavelength and is refracted the least. This is why blue is always at the bottom of the arc and have a larger curvature, whereas red is always at the top, with a smaller curvature.

彩虹是水滴折射太阳光而成。太阳光是不同颜色的可见光混合而成，每种颜色光的波长都不一样，因此折射率不一样，折射角度也不一样。蓝光波长最短，折射率和折射角度最高，因此蓝虹的弧度最大。红虹则反之。

A double rainbow, however, resulted from the the already refracted light reflected by the raindrop a second time before leaving the rain drop. This resulted in the colour being reversed.

而双彩虹已被折射的光在水滴中再反射才出来，因此亮度变低，颜色也反过来了。

To conclude, let's hear famous Taiwanese Artist Angela Zhang's beautiful cover of "Over the Rainbow":

最近因《歌手》再火起来的张韶涵第一张专辑的第一首歌就是《Over the Rainbow》哦！我们来听一下她甜美的演译吧: