Fog appears white because of the way light interacts with the water droplets suspended in the air that make up the fog.
Here's a breakdown:
- Light Scattering: Fog consists of tiny water droplets floating in the air. When light passes through fog, it encounters these droplets.
- Mie Scattering: The size of the water droplets in fog is roughly the same as the wavelengths of visible light. This causes a type of scattering called Mie scattering.
- Non-Selective Scattering: Mie scattering scatters all wavelengths of visible light (red, orange, yellow, green, blue, indigo, violet) more or less equally. Unlike Rayleigh scattering (which causes the sky to be blue), there's no preferential scattering of shorter wavelengths.
- White Light: Since all the colors of light are scattered in roughly equal amounts, the scattered light appears white to our eyes. This is because white light is a combination of all colors of the visible spectrum.
- Dense Barrier Effect: The numerous water droplets in fog create a dense barrier. This dense scattering of white light creates the opaque, white appearance we associate with fog.
In essence, fog looks white because it scatters all colors of light equally due to the size of the water droplets, creating a uniformly white appearance.
