Gallery: Lunar Halos, Septuple Rainbows and Iridescent Meat: Incredible Optics Photos
01lightning-spectra
Sometimes you catch an odd glint of light, see a colorful rainbow or spot a hazy mirage in the distance. All these are optical effects, where a distortion of light produces some incredible image. Optics is the branch of physics dealing with the behavior of light, how it interacts with matter and the way it reflects from and refracts through materials. For 14 years, the website [Optics Picture of the Day](http://www.atoptics.co.uk/opod.htm "Atmospheric Optics") has collected and featured stunning examples of these effects. The site’s owner, physicist Les Cowley, came to appreciate what light can do one cold afternoon back in the 1970s. “I was dragged outside the lab to see an [ice halo](http://www.atoptics.co.uk/halosim.htm) display,” he wrote in an e-mail. “The sky was webbed and crisscrossed with delicate arcs -- it was entrancing. I had no idea of their names or how they had formed but I was hooked on sky optics.” Cowley started OPOD back in 1998 to spread the message of sky optics and help explain how such phenomena form. Fairly soon, other interested photographers were submitting their own superb pictures. In this gallery, we look at some of the site's most amazing images and the physics underlying their eye-catching effects. __Above:__ ### Lightning Spectra In his celebrated 1704 book *[Opticks](http://www.rarebookroom.org/Control/nwtopt/index.html)*, Isaac Newton describes shining a white light through a prism. When the light emerged, the famous physicist was surprised to see it broken into a dazzling rainbow of colors. While this and other discoveries from Newton helped revolutionize the field of optics, it wasn’t until the 1800s that scientists understood how much information those rainbows contained. When passed through a prism, the light coming from a hot gas reveals its constituent elements in telltale lines of color. In this image, taken during a thunderstorm over Paris, the forking lightning bolt heats surrounding air to between 36,000 and 54,000 degrees Fahrenheit, breaking apart air molecules into ionized plasma. The bright lines of the spectra reveals the presence of nitrogen and hydrogen in our atmosphere. *Image: [Denis Joye](http://www.atoptics.co.uk/fz655.htm)*
02iridescent-meat
### Iridescent Meat Many optical effects come from distorting light. When waves of light are bent or reflected through some material or scatter off a surface, they can [interfere with one another](http://www.physicsclassroom.com/class/waves/u10l3c.cfm). The trough of one light wave cancels out the peak of another, or two peaks coincide, creating a brighter spot. With many wavelengths interacting, these effects can give rise to strange phenomena. In this picture of corned beef, the unappetizing colors come from the light waves bouncing off the sliced meat. When cut, the animal muscles of the meat protrude in a regularly spaced array, like a set of stairs, forming what is known as a diffraction grating. (Probably the most familiar diffraction grating is the back of a compact disc, which produces a rainbow pattern.) Light waves reflecting off the meat interfere with one another, giving rise to the odd prismatic colors seen in the image. The photographer of this picture, John Flyte, was able to turn the unexpected sighting into a lesson for his fifth-grade students: “It was St. Patrick’s Day 2011 and I wanted a traditional lunch so I ordered some freshly cut corned beef at the deli. When I got home and made a sandwich I saw green and was a little grossed out. Then I saw the reds, pinks, blues, as well as the shades of green. I recognized it as iridescence and only saw it once before at a banquet that had freshly cut roast beef. As a science teacher I was immediately fascinated and took pictures of it in natural light," Flyte wrote in an e-mail. "When \[Les Cowley\] printed my picture on his website, I showed my 5th grade classes and we started a great discussion on rainbows, optics, haloes, etc. It was one of those ‘teachable moments’ that teachers dream about. Websites like Mr. Cowley’s are great, and as I try to remind my students, ‘Science is everywhere, and every where there is usually a scientific story about it.’” *Image: [John Flyte Jr.](http://www.atoptics.co.uk/fz734.htm)*
03lunar-halo
### Lunar Halo The beautiful circle surrounding the moon in this image is caused by ice crystals suspended in the air. Known as a paraselenic circle, this rare phenomenon comes from moonlight [reflecting in complex ways](http://www.atoptics.co.uk/halo/pcpaths.htm) off the crystals. While the circle is commonly only seen in sections, in some cases, such as this one, it can stretch around the entire sky. A similar effect can occur on a chilly day with sunlight, forming a giant [parhelic circle](http://www.atoptics.co.uk/halo/parcirc.htm) in the sky. *Image: [Adam Kraft](http://www.atoptics.co.uk/fz739.htm)*
04tropical-rainbows
### Tropical Rainbows Serenity could be defined as a rainbow-filled tropical paradise. This image, taken in Sentani, Papua, Indonesia, comes pretty close to capturing this idyllic idea. But these iridescent thin clouds aren’t exactly producing rainbows. When a wave of light passes the tiny droplets of water in a cloud, it splits like water moving past a breaker. The two waves can then overlap and interfere, giving rise to the shimmering colors seen here. This tranquil image was rather a stroke of luck. “I was outside photographing insects,” wrote photographer Scott Frazier in an e-mail. “Suddenly the sky turned dark. Disappointed at first but I looked up, and this is what I saw! This fantastic optical phenomenon made a striking backdrop to a stand of “betel nut” palms (*Areca catechu*).” *Image: [Scott Frazier](http://www.atoptics.co.uk/fz707.htm)*
05glory-in-space
### Glory in Space While on a plane, you may have once looked out the window and seen the aircraft’s shadow on a cloud ringed by a perfect circular rainbow. This rainbow ring is called a glory. [Glories](http://www.atoptics.co.uk/droplets/gloab.htm) happen when the sun shines through a mist or cloud and the light gets scattered backward by individual droplets. They will appear around an observer’s shadow, which usually gets distorted and magnified into what is known as a “[Brocken spectre](http://www.atoptics.co.uk/droplets/globrock.htm).” This glory -- possibly the first spotted around an ascending spacecraft -- was seen trailing the Space Shuttle Atlantis after it launched on July 8, 2011. Atmospheric optics observer Rafael Schmall in Hungary and a group of friends who were watching the launch on live NASA TV saw the glory and notified the OPOD website. *Image: [NASA TV](http://www.atoptics.co.uk/fz648.htm)*
06septuple-rainbow
### Septuple Rainbow This image, taken in Strasbourg, France, features grey clouds framing an astounding rainbow with seven fainter rainbows trailing below it. This infrequent effect, called a [supernumerary rainbow](http://www.atoptics.co.uk/rainbows/supform.htm), comes about when the raindrops generating a rainbow are particularly uniform in size. As the different light waves spread out, they interfere with one another and form areas of darkness or brightness. These appear as pastel fringes below a regular rainbow. *Image: [Denis Betsch](http://www.atoptics.co.uk/fz696.htm)*
07prismatic-road-signs
### Prismatic Road Signs Road signs need to make their presence known rain or shine, dark or light. Even without the benefit of electricity, a road sign still catches a driver’s attention. They do this by reflecting light into a spectrum. Modern road signs are covered in small prisms and even lenses which bounce light directly back at a driver. The iridescent colors appear when sunlight or headlamp light is dispersed into its components by the tiny prism faces. *Image: [Denis Joye](http://www.atoptics.co.uk/fz711.htm)*
08lens-reflection
### Lens Reflection The glasses in this image appear normal, but their reflection in the table contains a multitude of psychedelic colors. This effect comes about because of interference in polarized light. Light is polarized when its electromagnetic waves are all oriented in the same way. Polarizing sunglasses, for instance, reduce glare by only allowing through a small percentage of light with the correct orientation. The polarized light emitted by a white LED monitor illuminates this picture. When the light passes through the glasses, it gets split into two beams. Once these two beams bounce off the table, they interfere with one another, producing odd swirls of color in the reflection. *Image: [John Moore](http://www.atoptics.co.uk/fz678.htm)*
09water-strider-optics
### Water Strider Optics Those dark spots sitting underneath this water strider aren’t exactly shadows. They're patches of darkness created from distorted light as the little insect walks on the water’s surface. A shallow pond’s surface acts somewhat like a stretched elastic skin. Water striders (of the family *Gerridae*) are able to “walk” on top of this skin because the surface tension produces a small upward thrust that holds their tiny weight. The insect’s feet depress the water’s surface, producing a dip that bends light rays away from it. This creates a zone where no light can reach. Reflected rays all get pulled together, creating an intensely bright rim around each darkened patch. *Image: [Andrew Kirk](http://www.atoptics.co.uk/fz677.htm)*
