Why the blue sky is blue and polarised
The Earth's atmosphere is illuminated by the sun, which light is scattered throughout the atmosphere. Blue light is scattered most and hence cloudless skies are blue. But they are also highly polarised due to the same scattering process.
How polarised light enables us to investigate dust in the atmosphere
Dust in the air causes all kinds of health problems. Is is usually hard to see such dust, but by measuring the polarisation signature that it imprints on sunlight, we can now detect hazardous dust and figure out its properties.
How polarising sunglasses help us reject the glare of sunlight
Many sunglasses have built-in polarisation technology. This is particularly useful for rejecting sunlight that for is instance reflected by water on the road.
The polarisation of rainbows
Rainbows are not only beautiful, they are also polarised. The polarisation of rainbows and other atmospheric effects like halos provides important clues to how these phenomena work.
Why clouds are white and not so much polarised
Clouds consist of tiny water droplets, which are yet still much larger than the air molecules that make the blue sky blue. The scattering properties of cloud particles are therefore very different from air molecules, and hence clouds stand out prominently white against the blue sky. Also their polarisation properties are very different.
How polarisation colors car windows
Drivers that wear polarising sunglasses often see all kinds of colors in their windscreen. This is not an illusion but a very real polarisation effect that exposes the way the windscreen was fabricated.