In-flight Optics

Last updated on September 16, 2023

In-flight Optics: Discovering the Wonders of the Skies

When we find ourselves in the window seat of an airplane, soaring through the high-altitude skies, we are presented with a unique opportunity to witness a plethora of mesmerizing optical effects. Beyond the breathtaking landscapes below, the heavens above offer a spectacle of glories, opposition glows, ice halos both above and below the horizon, flattened suns and moons, long shadows, and even extraordinary dark and purple skies. However, the captivating world of in-flight optics doesn't end there. Even inside the cabin, there are optical phenomena that can help us pass the time in awe-inspiring ways.

Orange Juice Caustics: Nature's Masterpiece

One such phenomenon that can captivate our attention during a flight is the mesmerizing display of orange juice caustics. When sunlight hits the curved surface of a plastic cup, the rays reflect and converge at a particular point, forming sharp surfaces of bright light known as caustics. These caustics create a stunning visual effect where the concentrated rays meet. The same phenomenon can be observed with a sunlit coffee or tea cup. It's a reminder that even everyday objects can unveil extraordinary beauty when illuminated by sunlight.

To better understand this phenomenon, let's take a closer look at a computed ray diagram. The caustics are tangent to each reflected ray and indicate the areas where the ray concentration is greatest. These curves intersect at a cusp, creating a visual spectacle that adds a touch of magic to our in-flight experience.

Unveiling the Secrets of Diffraction

The micro ridges present on the surface of the cup play a crucial role in producing the vibrant colors we observe during this optical phenomenon. Acting as a diffraction grating, these tiny ridges cause the light to diffract, resulting in a stunning array of colors that dance before our eyes. It's a reminder that even the most seemingly mundane objects can reveal hidden secrets when examined closely.

Vibrations: Adding a Ripple of Wonder

As we marvel at the ever-changing reflection of the sun on the surface of the orange juice, another element comes into play: the vibrations of the aircraft. These vibrations create additional caustics and reflection patterns, adding another layer of fascination to the scene. The occasional concentric ripples that appear on the surface of the juice further enhance the visual spectacle, resembling the mesmerizing effects created by T-Rex in Jurassic Park.

Conclusion: Embracing the Beauty of In-flight Optics

In-flight optics is a world waiting to be explored, filled with wonders that can captivate our senses and ignite our curiosity. From the enchanting display of orange juice caustics to the intricate dance of diffracted light, every moment spent in the window seat presents an opportunity for discovery. Whether we find ourselves gazing at the captivating colors produced by diffraction or marveling at the ever-changing reflections caused by vibrations, the skies above and the cabin around us are brimming with beauty and optical phenomena waiting to be observed. So next time you find yourself soaring through the clouds, remember to look beyond the window and embrace the enchanting world of in-flight optics.

In-flight Optics

Alan Clark took these photos during a flight across Canada.

If you have a window seat, the high altitude skies provide many optical effects. There are glories, opposition glows, above and below horizon ice halos, flattened suns and moons, long shadows and extraordinary dark and purple skies.

Alan also found plenty of optics inside the cabin to help while away the hours.

Image ©Alan Clark, shown with permission

Orange Juice Caustics

The juice is lit by two curves met at a cusp. These are caustics, sharp surfaces of bright light formed where there is a high concentration of rays. Sun rays reflect from the plastic cupos curved surface before splashing on the juice surface. A sunlit coffee or tea cup has them too.

At right: A computed ray diagram. The caustics are tangent to each reflected ray and mark the location where the ray concentration is greatest.

Diffraction

Micro ridges on the cup act as a diffraction grating to produce these colours.

Vibrations, vibrations..

Alan watched the ever changing sun's reflection from the orange juice projected onto a seat back. Aircraft vibrations produced yet more caustics, more reflection caustics. Their appearance suggests occasional concentric ripples on the juice surface.

Pure concentric ripples are not easy to generate - watch this re-creation of those made by T-Rex in Jurassic Park.

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