Question

Why does the sun appear red during sunrise and sunset?

Answer 1

Hint: Red light has maximum wavelength in the visible spectrum.

Complete step by step answer:
The light from the sun has to travel more distance to reach our eyes during sunset and sunrise compared to other times of the day. So the visible light which consists of multiple wavelengths has to travel a longer distance, which means it has to interact with more number of particles compared with other parts of the day. When these wavelengths interact with atoms in the atmosphere some of the frequencies get absorbed and rest is reflected or transmitted. In other words, the light travelling through the atmospheric medium gets scattered and only the wavelength which is not scattered reaches our eyes.
So high frequency (low wavelength) gets easily scattered compared to the low frequency (high wavelength) light. So the blue region of the visible spectrum which has a higher frequency gets scattered faster compared to the red region of spectrum. During sunset or sunrise a large amount of visible light is scattered off with only the longer wavelength region which consists of orange and red wavelengths reaching our eyes.

Note: Scattering is the reason for the Tyndall effect, which involves the scattering of light by fine particles present in a colloid or a suspension.
The gloss or lustre of a surface is determined by scattering.
There are three main types of scattering that impact light. They are Rayleigh scattering, Mei scattering and Non-selective scattering