Higher Order Bows

Last updated on September 16, 2023

Higher Order Bows: Unveiling the Hidden Beauty of Atmospheric Optics

When we think of rainbows, we often picture the familiar arc of colors stretching across the sky. But did you know that there are more than just primary and secondary rainbows? Welcome to the world of higher order bows, where each additional reflection inside raindrops creates a unique and captivating spectacle.

The Progressive Faintness and Broadening of Higher Order Bows

As light undergoes multiple internal reflections within raindrops, it gives rise to higher order bows. However, unlike their prominent counterparts, these bows appear progressively fainter and broader. This diminishing brightness is a result of each reflection diminishing the rays, causing their surface brightness to be further reduced. It's a delicate interplay between light and water droplets that brings forth these ethereal displays.

A Rare Sight: Observing Higher Order Bows

While primary and secondary rainbows grace the skies with their presence, higher order bows remain a more elusive phenomenon. Only bows resulting from one and two reflections, as well as the zero order glow, have been reliably sighted. These higher order rainbows do not occur in any orderly sequence but can be found both sunward and opposite the sun.

The Dance of Light: Positioning of Higher Order Bows

The positioning of higher order bows is an intricate dance between sunlight and water droplets. Bows resulting from one and two internal reflections of the primary and secondary bows send light back towards the sun. As a result, these bows appear opposite the sun and are centered on the antisolar point. On the other hand, three and four reflections direct light forward, creating bows that encircle the sun. Fifth and sixth order bows, like their primary and secondary counterparts, scatter light backward and appear opposite the sun.

The Weakening of Rays: A Subtle Beauty

With each internal reflection, the rays within higher order bows gradually lose their strength, resulting in their progressive faintness. Additionally, the entrance ray that forms each bow grazes closer and closer to the edge of the raindrop. This phenomenon causes the colors within higher order bows to spread wider, further reducing their brightness. It's a delicate balance between the intricate path of light and the properties of water droplets that creates these mesmerizing displays.

Exploring the Wonders of Atmospheric Optics

As we delve into the world of higher order bows, we uncover the hidden beauty of atmospheric optics. These captivating phenomena remind us of the complexity and wonder present in our natural surroundings. By observing and understanding these optical phenomena, we gain insights into the interplay between light and the environment, shedding light on the intricate workings of our atmosphere.

Embracing the Ephemeral

Higher order bows serve as a reminder of the ephemeral nature of atmospheric optics. Their rarity and subtle appearance make them a true treasure for those fortunate enough to witness them. As we gaze upon these delicate displays, we are reminded of the ever-changing nature of our world and the fleeting moments of beauty that grace our skies.

In conclusion, higher order bows reveal a world beyond the familiar primary and secondary rainbows. These ethereal spectacles, born from multiple internal reflections within raindrops, captivate our senses with their progressive faintness and broadening. While they may be elusive and rare, their presence reminds us of the intricate dance between light and water droplets that shapes our atmospheric optics. So, next time you find yourself gazing at the sky after a rainfall, keep an eye out for these hidden gems and embrace the wonders of higher order bows.

Rays of the first six rainbow orders

Each extra reflection inside the raindrops produces a different rainbow.

The higher order bows get progressively fainter because each reflection dims the rays. They also get broader and hence their surface brightness is even further reduced.

Only those from one and two reflections and the zero order glow have ever been reliably sighted in the sky.

Rainbows all over the sky - High order rainbows do not occur in any orderly sequence. They lie both sunward and opposite the sun (see an all-sky simulation).

The one and two internal reflections of the primary and secondary bows send light back towards the sun and hence their bows appear opposite the sun and centered on the antisolar point.

Three and four reflections send light forwards to give bows that circle the sun. 5th and 6th order bow rays are backward scattered and they occur opposite the sun like their primary and secondary counterparts.

Each internal reflection weakens the rays and the higher order bows are progressively fainter. Look also at how the entrance ray that makes each bow grazes closer and closer to the edge of the drop. This makes the higher order bow colours spread wider and reduces their brightness even further.

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Reference Atmospheric Optics

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