During the summer, especially during the holidays, we can observe quite often the days with blue sky and the sunset, when the sky fills with red and orange tones. But how does this color change happen?

Waves of Light

This change of color in the sky happens mainly because of the way the light spreads in the atmosphere. This is because sunlight comes to Earth through electromagnetic waves of different wavelengths, the smaller wavelengths are blue and the wavelengths are red.

Sunlight is white, however, when it encounters the particles present in the atmosphere, it undergoes scattering. The smaller wavelength radiation spreads more easily, while the longer wavelength radiation  don’t cross over the atmosphere. The light that strikes our eyes is the light scattered and so we see the sky with the color blue.

But how does the sky turn red?

It’s simple. In the late afternoon, when the sun is near the horizon, sunlight needs to cross much more atmosphere to reach us. In this way, the blue waves, of small wavelengths, undergo scattering until reaching the light that crossed the atmospheric layer, that is, those of greater wavelength that correspond to the colors red, orange and yellow.

Do you want to understand a bit more about optical physics? With the Alpha Optical Bank you can do various studies and experiments.