Rainbows
Rainbows have always fascinated humans. In fact, different societies explore the meaning of the rainbow through various myths and legends. While certain cultures have regarded the rainbow as a link to the heavens and the afterlife - a positive source of inspiration, other cultures have viewed this earthly light show as a bad omen - forecasting even death.
Scientists, too, have been struck by the beauty of the rainbow, and Rene Descartes in 1637 discussed the optics of this phenomenon by reducing the rainbow to a study of a single water droplet and how light interacts with it.
As sunlight passes through a water droplet, it gets refracted, while in the raindrop it gets reflected and then upon its exit the light once more gets refracted. Some of the light leaves the same side that it entered.
The light of the sun is comprised in part of a continuum of colours, from red to violet and all colours in between. When combined, to our eye, sunlight appears as white light. However, when sunlight passes from one medium to another, in this instance as it passes from air to water and back to air once more, the process of refraction and reflection split this white light into the colours of the spectrum.
The longer light waves, those that we see as red, do not get bent as much as the shorter light waves, those that we see as blue. When it rains and the sun is out, the sunlight enters the countless raindrops, and through the process of reflection and refraction splits the white light, producing the bands of colour that we see as the rainbow.
The sun is always behind the observer of the rainbow, and all rainbows are unique to their observers.
The size of the water droplets influences the rainbows that emerge. The bigger the raindrops the brighter the rainbow. The smaller droplets of water produce the fainter bluer colours. |
