Disappearing Indradhanush

Rainbow is very aptly called “IndraDhanush” in Indian mythology as Indra is the God of rain and once he showers his blessings on us he hangs his Dhanush (bow) in the sky to rest till his next rain-assignment.

Rainbow is used as a symbol of   hope, harmony happiness , peace and prosperity.  Occasionally, rainbows are observed in double arcs as in the above photograph. While we were growing up we had plenty of opportunity to view rainbows including . Standing with sun behind and looking at a light showers. Raindrops, rather than the cloud droplets, normally form rainbows by splitting up the light in its constituent colors.

Now if I give it a thought rainbow has become a rarity. Had to wait almost 10 years to show it to my kid. Maybe I missed it due to work but kid also didn’t see any while playing out or in school . Why is this amazing natural phenomenon disappearing? – “Pollution”.

Few years ago a Korean scientist had shown that due to air pollution the phenomenon of rainbow does not take place anymore in his city. That’s the reason we didn’t see any for long and double arcs are gone now. Now we only see rainbows while travelling on a highway away from urban settlements  or when pollution is washed off completely by heavy showers.

Recently we saw it while travelling on a highway in eastern ghats. It was so grand and beautiful that people where stopping to click and save it for future generations

Pollution affects rainbow and recently its proposed to use it in determining the air quality and type of pollution by  Alexander Haußmann, of the Technical University of Dresden, Germany. The  size of a rainbow can tell scientists if there are chemicals in the atmosphere. Because chemicals — like acid rain, for example — change the makeup of the water droplets, the sunlight reacts differently as it passes through them and shrinks the rainbow’s radius.  If you have pollution particles in the air, they can change the scattering so that less vivid colours are observed.

Rare double and triple rainbows are caused by light rays reflecting twice or thrice inside the droplet and are directly elated to the size of the droplet. Pollution can reduce the size of droplets to the extent that reflection and refraction doesn’t take place or interfere in the condensation process it self. Particles, especially black carbons, are known to absorb visible range spectrum mostly. This light-absorbing substances in the atmosphere can be responsible for the brown appearance of urban haze and the discoloration of the sky. I once happened to talk to a mining engineer relative who spent his life working in the coal mines of India and stayed in colliery’s. He never observed rainbow all his life even though he lived far away from cities.  Other particles in air  too attenuate sections of visible spectrum.

Though its a complex process but one thing is sure we are having more and more air pollution for last few years and this great phenomenon is getting rarer .





A physicist turned green living advocate.

Welcome! Fellow Green Living Enthusiast

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