Scattering of light
Intermediate
Rayleigh scattering makes the sky blue.
I ∝ 1/λ⁴Molecules scatter light with intensity ∝ 1/λ⁴ (Rayleigh): blue sky and red sunsets. Larger particles scatter all colours (white clouds).
Blue scatters 5.5 times more than red.
Scattering is not the same as reflection.
In more detail
Light is scattered by particles in the atmosphere, with shorter wavelengths scattered more strongly, as in Rayleigh scattering. This explains why the sky is blue and sunsets are red.
Real-world uses
- Sky colour is used in weather and atmospheric studies.
- Scattering measures particle size in aerosols and clouds.
- The sky looks blue because shorter wavelengths are scattered more strongly by air molecules.
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Frequently asked questions
Why is the sky blue?
Shorter blue wavelengths are scattered more strongly by air molecules.
Why are sunsets red?
Light travels through more air at low angles, scattering away the blue and leaving red.
Why are sunsets red?
Light passes through more air at sunset, so most of the blue is scattered away and the reds reach the eye.
Related topics in Optics
Prism and deviation · Dispersion · Rainbow formation · Mirage · Refraction at a spherical surface · Thin lens