Green light - Ryokko

Japanese: 緑光 - りょっこう

Green flash is also called green flash. It is a phenomenon in which the part of the sun's disk above the horizon at sunrise and sunset appears green. The angle at which sunlight refracts as it passes through the atmosphere is particularly large when the sun is near the horizon. Meanwhile, the refractive index differs depending on the wavelength of light, with blue light being more refracted and red light being less refracted. Therefore, at sunrise and sunset, light is significantly dispersed, and the blue and red light travel in different directions at angles of about 20 to 40 minutes, resulting in the appearance of green light.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

緑閃光（りよくせんこう），グリーンフラッシュgreen flashともいう。日の出，日没時に水平線上に出ている太陽面の部分が緑色に見える現象。太陽の光が大気を通った時に屈折する角度は，太陽が水平線付近にある時に特に大きい。一方，屈折率は光の波長によってちがい，青の方が屈折が大きく，赤の方が屈折が小さい。したがって日の出，日没時には，光の分散が著しくおこり，青と赤の光はその進む方向が角度で20～40分ぐらいちがって，緑光が見られる。

出典　株式会社平凡社世界大百科事典第２版について　情報

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