Smoky Mountains Fogbow

Last updated on September 16, 2023

Smoky Mountains Fogbow: A Phenomenon of Atmospheric Optics

Have you ever witnessed a mesmerizing display of light in the misty mountains? One such captivating phenomenon is the Smoky Mountains Fogbow. Similar to rainbows, fogbows are centered opposite the sun on the antisolar point. However, there are significant differences between the two. In this article, we will delve deeper into the enchanting world of fogbows and explore the unique characteristics of the Smoky Mountains Fogbow.

Searching for the Smoky Mountains Fogbow

To catch a glimpse of the elusive Smoky Mountains Fogbow, it is best to observe when the sun breaks through the mist. Position yourself with the sun at your back and look at an angle of approximately 35-40 degrees from the shadow of your head. This angle is roughly equivalent to the width of two outstretched hands held at arm's length. While fogbows may have low contrast, keep an eye out for small brightenings in the misty background. Once you spot a fogbow, it becomes unmistakable, captivating your senses with its ethereal beauty.

The Formation of Fogbows

Fogbows form in a similar manner to rainbows, but with distinct differences. Both rainbows and fogbows occur due to the interaction of sunlight with water droplets. However, rainbows are formed by raindrops, which are relatively larger and allow rays of light to follow well-defined paths known as "geometrical optics." In contrast, fogbows are formed by much smaller droplets that diffract light extensively, resulting in a diffuse and broad bow.

When light enters these tiny droplets, a small fraction of it is internally reflected once before emerging. This emergent light forms a large circle opposite the sun, creating the fogbow. The main fogbow typically has a radius ranging from 30 to 45 degrees.

The Unique Characteristics of the Smoky Mountains Fogbow

The Smoky Mountains Fogbow, like other fogbows, exhibits a deviation of light. The emergent light is mostly deviated approximately 135 to 150 degrees from its incident direction, contributing to the formation of the main fogbow. This deviation corresponds roughly to the angle of minimum deviation (~138 degrees) observed in the geometric optics of rainbows with a radius of 42 degrees.

What sets the Smoky Mountains Fogbow apart is its captivating presence amidst the mist-shrouded peaks. As sunlight breaks through the atmospheric haze, the fogbow emerges as a ethereal halo, adding an enchanting touch to the already breathtaking landscape. Its diffuse and broad appearance creates an otherworldly ambiance, captivating all who are fortunate enough to witness it.

The Fascination of Atmospheric Optics

The study of atmospheric optics unveils the hidden beauty of nature's light displays. From rainbows to fogbows, each phenomenon offers a unique perspective into the interaction between sunlight and water droplets. By understanding the intricate workings of these optical marvels, we gain a deeper appreciation for the wonders that surround us.

Conclusion

The Smoky Mountains Fogbow is a captivating example of atmospheric optics, showcasing the mesmerizing interplay between sunlight and mist. As you explore the misty mountains, keep an eye out for this enchanting phenomenon. Remember to position yourself with the sun at your back and look at an angle of approximately 35-40 degrees from the shadow of your head. With a bit of luck and timing, you may find yourself standing in awe of the ethereal beauty of the Smoky Mountains Fogbow.

Fogbow, Great Smoky Mountains, Tennessee imaged by Chris Ewing (photography) on last Christmas morning. ©Chris Ewing, shown with permission.

Fogbows like rainbows are centered opposite the sun on the antisolar point.

They are best searched for when the sun breaks through mist. With the sun at your back look at an angle of 35-40� from the shadow of your head. A little less than the width of two outstretched hands held at arm's lengths roughly gives the angle. Many fogbows have very low contrast so look for small brightenings in the misty background. Once caught, they are unmistakable.

Fogbows form in the same way as rainbows. A small fraction of the light entering droplets is internally reflected once and then emerges to form a large circle opposite the sun.

Beyond that there are major differences. Rainbows are formed by raindrops which are so large that rays passing through them follow well defined 'geometrical optics' paths. Fogbows are formed by much smaller droplets which diffract light extensively. The resulting bow is diffuse and broad.

The emergent light is mostly deviated 135 to 150� from its incident direction to produce the main fogbow of 30 - 45� radius. The deviation corresponds roughly to the geometric optics angle of minimum deviation of ~138� for the 42� radius rainbow.

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Reference Atmospheric Optics

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