美丽的霓虹-双彩虹
这次去西藏的时候看到了双彩虹,现在来整理下思路:
1. 一般的彩虹只涉及到水珠内两次折射(refraction)一次反射(reflection). 并且太阳光和人眼视角夹角要小于42度左右才可以看见.
Light rays enter a raindrop from one direction (typically a straight line from the Sun), reflect off the back of the raindrop, and fan out as they leave the raindrop. The light leaving the rainbow is spread over a wide angle, with a maximum intensity at 40.89–42°. |
White light separates into different colours on entering the raindrop because red light is refracted by a lesser angle than blue light. On leaving the raindrop, the red rays have turned through a smaller angle than the blue rays, producing a rainbow. |
2. 因为色散, 一般的彩虹从上到下是红到蓝, 并且红色比蓝色展的要宽.(蓝光反射后的角度要大过红光,所以蓝色在下面)
3. 双彩虹的出现涉及到水珠内的两次反射(two internal reflection)s以及两次折射,因此能量损失不少,颜色要黯淡(fainter). 此外颜色排布反转. (the order of the colored disks produced by the raindrops is reversed, with red light at the bottom and blue light at the top of the secondary rainbow). p.s., 第二道彩虹通常叫做”霓”.
4. 霓在虹的上面是因为高处的水珠才会造成入射光线的两次反射
5. 主彩虹下面的区域很明亮,上面则要黯淡.(the light is bright below the primary rainbow), 这是因为彩虹内部的区域,光线大多直接反射回来.
下面请大家欣赏本人原创作品—双彩虹:
