During sunries and sunset, sun appears raddish- orange because

The reddish-orange appearance of the sun during sunrise and sunset is primarily due to Rayleigh scattering. Atmospheric molecules and fine particles scatter shorter wavelengths (blue and violet) much more effectively than longer wavelengths (red and orange) [4]. At sunrise and sunset, sunlight travels through a significantly longer path in the Earth's atmosphere compared to noon. During this extended journey, most of the blue light is scattered away from the line of sight [1]. Consequently, the light that reaches the observer's eyes is predominantly composed of the least scattered longer wavelengths, specifically red and orange [1]. This selective scattering process, where scattering intensity is inversely proportional to the fourth power of the wavelength, ensures that the direct beam of sunlight is enriched in reddish hues when the sun is near the horizon.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 10: The Human Eye and the Colourful World > 10.6.2 Why is the colour of the clear Sky Blue? > p. 169
2. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 21: Horizontal Distribution of Temperature > Transparency of Atmosphere > p. 283