Why does the sun appear red at sunrise?
During sunrise, the sun is near the horizon. At this time the sunlight has to travel a longer distance through the atmosphere to reach our eyes. During this advancement, the sunlight gets scattered by the minute particles in the atmosphere. As the wavelength of the blue light is shorter, it scatters the most and can't reach us. The wavelength of red light is comparatively longer and hence it suffers less scattering. Therefore, the light that is reaching us contains mostly the red colour. That is why the sun appears red during sunrise.