What is in a rainbow?

Last few months I have been so lucky to spot many rainbows. Every time I spot a rainbow I remind myself that it is a nature’s way of playing a musical scale with lights. Many years ago out of curiosity to write a program to generate musical notes I found out that the frequency of musical notes were not linear steps instead it is ratios. The next octave’s frequency is double the frequency of current octave and it is achieved through 12 steps, the ratio between two subsequent steps is always the same, it is 12th root of 2 which is roughly 1.059.

If we consider C note to be 400 Hz then the mid point in the octave is G note which is 600 Hz and the next Octave C note is 800 Hz. While going through this learning stumbled across somewhere that our eyes are more sensitive than our ears as ears listen to around 10 octaves of sound but eyes see only one octave so it can differentiate frequencies better than ears.

Took wikipedia’s help to map out the frequencies I listed above to colours. Red is 400THz and Ultra Violet is 800 THz. So got the frequencies from the piano and mapped it to colours. It mapped to a rainbow, red to yellow continuum mapped little loosely compared to green to violet.

The equivalent carnatic ragam to this scale is Shulini which in Hindu mythology means Durga, the adi shakti (Divine Pure Eternal Consciousness) — the mother of all universes. It may not be a coincidence that the light spectrum equivalent in music is named after the Zero energy. More can be read here about the modern interpretation of adi shakti.

What is in a rainbow? It gave me goosebumps when I stumbled on this.