很多人都见过彩虹。彩虹最常在下午,雨后刚转晴时出现。我们通常看到的彩虹都是拱形的,就像一座横跨在天空中的彩色桥梁。不过下面这些特别的彩虹,大家可能就很少看到哦。环形彩虹其实大多数的彩虹都是一个完美的圆环形,但是我们很难看到完整的环形彩虹。这是因为彩虹总有一半在地平线以下,被地面遮挡,所以我们看到的彩虹大多数都是一个半弧。但是如果我们在观察彩虹时站得足够高,比方说站在视野开阔的高山之巅,或者 Many people have seen the rainbow. The rainbow is most often seen in the afternoon, when the rain has just turned fine. The rainbow we usually see is arched, like a colored bridge across the sky. But below these special rainbow, everybody may seldom see oh. Rainbow ring In fact, most of the rainbow is a perfect ring, but we can hardly see the full annular rainbow. This is because there are always half of the rainbow below the horizon, covered by the ground, so most of the rainbow we see is a half-arc. But if we stand tall enough to observe the rainbow, say to stand on the top of a mountain of vision, or