Explanation:

The phenomenon responsible for the reddish appearance of the Sun during sunrise and sunset is scattering of light, more specifically, Rayleigh scattering. When the Sun is near the horizon at sunrise and sunset, sunlight travels through a greater thickness of the Earth's atmosphere, and it scatters more short-wavelength (blue and violet) light. This scattering of shorter wavelengths of light allows the longer wavelengths (red, orange, and yellow) to reach our eyes, making the Sun appear reddish.