Great Wall Bow

Last updated on September 16, 2023

The Great Wall Bow: A Spectacular Atmospheric Phenomenon

Have you ever heard of the Great Wall Bow? This awe-inspiring atmospheric optics phenomenon occurs at the majestic Great Wall of China, specifically in the Jinshanling section. While the Great Wall itself is renowned for its historical significance and architectural grandeur, it also offers a unique treat for those fortunate enough to witness it - the Great Wall Bow. In this article, we will delve into the fascinating details of this natural wonder and explore the science behind its captivating beauty.

Unveiling the Great Wall Bow

The Great Wall Bow refers to the appearance of rainbows at the Great Wall, created by the interaction of sunlight and raindrops in the surrounding atmosphere. When a brief shower passes over the area, the raindrops act as tiny prisms, dispersing sunlight into its component colors. As a result, vibrant rainbows materialize, stretching across the valley below the wall. It's truly a breathtaking sight to behold!

The Science Behind the Great Wall Bow

To understand the science behind the Great Wall Bow, let's dive into the intricate workings of rainbows. Rainbows are formed when sunlight enters a raindrop, undergoes multiple internal reflections, and finally exits the drop as a beautiful arc of colors. Each raindrop contributes to the overall display, creating a mesmerizing tapestry of hues.

In the case of the Great Wall Bow, two rainbows often appear - the primary and secondary bows. The primary bow is the brighter and more prominent of the two. It forms when sunlight undergoes two internal reflections within a raindrop before exiting. The secondary bow is fainter and appears at a wider angle from the sun. It results from three internal reflections within a raindrop.

Exploring the Phenomenon

When observing the Great Wall Bow, one may notice intriguing characteristics that add to its allure. Here are some fascinating aspects of this phenomenon:

• The bright inner primary bow exhibits a distinct feature - the background inside it appears brighter. This occurs because raindrops within this region scatter sunlight to the observer's eye and camera at a greater angular deflection than the minimum rainbow angle. The primary bow takes the form of a disk of light, with its edge being brighter due to classical ray theory predicting infinite intensity at the rainbow rim, resembling caustics.

• Between the primary and secondary bows lies an intriguing region known as Alexander's Dark Band. In this area, raindrops are unable to direct any light towards the observer, resulting in darkness. This phenomenon adds a captivating contrast to the overall rainbow display.

Unlocking the Mysteries of the Great Wall Bow

While we can appreciate the beauty of the Great Wall Bow, it is equally intriguing to explore the scientific principles that govern its formation. Understanding these phenomena can deepen our appreciation for the wonders of nature. Here are some additional insights into the mysteries of the Great Wall Bow:

• The appearance of rainbows is not dependent on the distance of the shower producing the raindrops. Even if the shower is relatively close to the observer, the resulting rainbows will look the same. This is because rainbows are purely collections of light rays and their appearance remains consistent regardless of distance.

• The Great Wall Bow serves as a reminder of the fascinating interplay between sunlight and water droplets in our atmosphere. As sunlight passes through raindrops, it undergoes dispersion, revealing the full spectrum of colors that compose white light. This dispersion creates the vivid hues we see in rainbows.

Conclusion

The Great Wall Bow is an enchanting spectacle that adds an extra touch of magic to the already captivating Great Wall of China. The interplay between sunlight, raindrops, and our atmosphere creates a breathtaking display of colors that span across the valley beneath the wall. Understanding the science behind this phenomenon allows us to appreciate the intricate workings of nature and the remarkable beauty it bestows upon us. So, if you ever find yourself at the Great Wall, keep an eye out for the Great Wall Bow - a truly unforgettable experience!

Great Wall Rainbows imaged by Mark Vranicar (China blog) July 1st on a hike from the Jinshanling section of the Great Wall. ©Mark Vranicar, shown with permission.

The 'Great Wall' is a number of walls constructed from ~656 BC through to the 17th Century. This section was built in the Ming Dynasty (1368 - 1644) and is one of the best preserved. It includes 100 watchtowers as it strides over the mountains Northeast of Beijing.

Two rainbows created by a brief shower span the valley. The raindrops were relatively close but the rainbows, purely collections of light rays, look the same regardless of the shower's distance.

The background inside the bright inner primary bow is noticeably brighter. There, raindrops scatter sunlight to the eye and camera with a greater angular deflection than the minimum rainbow angle. The bow is a disk of light brighter at its edge. Classical ray theory actually predicts infinite intensity at the rainbow rim - a characteristic of caustics (1,2,3).

Between the primary and the fainter outer secondary is darkness. In that region the raindrops cannot direct any light towards the camera. This is Alexander's Dark Band.

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