When the Sun is near the horizon during the morning or evening, it app

When the Sun is near the horizon during the morning or evening, it appears reddish. The phenomenon that is responsible for this observation is

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reflection of light

refraction of light

dispersion of light

scattering of light

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This question was previously asked in

UPSC CDS-1 – 2018

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The phenomenon responsible for the reddish appearance of the Sun near the horizon is scattering of light, specifically Rayleigh scattering. As sunlight passes through a longer path in the Earth’s atmosphere during sunrise or sunset, shorter wavelengths (blue and violet) are scattered away more effectively by air molecules than longer wavelengths (red and orange). The light that reaches the observer’s eyes is therefore enriched in the longer, redder wavelengths.

– Rayleigh scattering is inversely proportional to the fourth power of the wavelength (scattering ∝ 1/λ⁴), meaning shorter wavelengths are scattered much more than longer wavelengths.
– The path length of sunlight through the atmosphere is longest at sunrise and sunset.

Reflection is the bouncing of light off a surface. Refraction is the bending of light as it passes from one medium to another (e.g., causing the sun’s image to appear flattened at the horizon). Dispersion is the splitting of white light into its constituent colors based on wavelength (as in a prism or rainbow). While these phenomena occur, scattering is the primary reason for the reddish appearance of the sun and sky color variations.

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