The red light has longer wavelenght than blue light.shorter wavelenght scatter finer particles while longer wavelengths scatter larger particles.during the sunrise and sunset , the sun is near the horizon.and so the sun light has to pass thicker layers of air.these layers have larger particles than noon.these large particles scatter red light as it has long wavelenght among the seven colors.thus, the larger particles and longer distance to be travelled by the sunlight to reach our eyes makes it appear red.

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