Red aurora are generated by light emitted at a longer wavelength (0.630 micrometers), and other colors such as blue and purple are also sometimes observed.
红色的极光是由较长波长(0.630微米)的发出光引起的，有时也会观察到其他诸如蓝色和紫色的极光。
I thought I was going to get this bike with seven gears and one of them razorblade saddles and purple paint and everything, and they gave me this light blue one.
第一个声音很权威地总结道，“我本以为会得到一辆七变速自行车，有剃刀式流线形座子、紫色涂装和一切的一切。 结果他们给了我—辆天蓝色的。
Under UV light, clean sand appears purple or black. Some minerals, such as calcium carbonate in seashells, glow blue, as does a shovel handle in the picture above.
紫外线照射下，干净的沙子呈紫色或黑色。有些矿物，如海贝中的碳酸钙，会闪着蓝光，就如同上图中的铁锹的把手。
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