Can you work out what these enigmatic close-up photos are of?

PAGE 20 MOMENT A while ago, I borrowed a piece of opal from a geological museum to photograph for a book I was working on. Using my ?real? camera, I had to figure out a good composition for a picture of this complicated mineral. Notice the larger light-blue ?veins? running across the image. I used them as organizational elements, to create sections to help the viewer decide how to look at the image. PHENOMENON Over many years of geological time, opal is slowly formed as many small spheres of silica (what glass is made of) self-assemble into perfectly ordered layers. Diffraction (not to be confused with refraction) occurs when light passes through the spheres and gaps, and it is split into the colors of the visible spectrum: red, orange, yellow, green, blue, indigo, and violet. The diameter of the spheres and the spacing between them determines the colors that we see. Light reflected from the different stacked layers creates interference effects.

These beautiful, enigmatic images were captured by scientist and photographer Felice Frankel in her everyday life. Before you read further, see if you can tell what they depict – we’ll reveal all below each photograph.

The images appear in Frankel’s new book Phenomenal Moments: Revealing the hidden science around us. Each close-up, many of which were taken on her phone, comes with an explanation of the scientific processes depicted. “It’s like a guessing game,” she writes.

Page 94 MOMENT While saut?ing yellow, orange, red, and green peppers for a pasta dish on my induction stove, the glass cover on my pan began to reflect all the wonderful colors. I ran to get my phone to make the image. There are times when we have to act quickly in order to capture something that might never happen again or could be fleeting. PHENOMENON Heat from the cooking surface caused the water from the peppers to vaporize, creating steam that was captured by the glass cover. The water coalesced into larger drops, forming condensation on the glass. The droplets act like lenses, transmitting the colors from the peppers onto the glass.

So, to the answers… The main image at the top of this article is a piece of opal – the blue lines are veins in the mineral. Light is diffracted as it passes through the stone, and the diameter of the small spheres of silica that make up its layers, plus the spacing between those spheres, determine which colours we see.

The image just above was taken when Frankel was sautéing peppers, as condensation formed on the pan lid. These tiny droplets acted like lenses and transmitted the colour of the peppers through the lid and into her camera.

Page 121 MOMENT This second image was the picture I was reminded of when studying the pollen grains. I placed the whole 2-inch (5-centimeter) sample of agate on my scanner and captured the image at a high resolution, knowing that I would crop in to make an interesting final image. PHENOMENON This detail of the mineral agate was also formed by layering, or banding. In this case, the material is called chalcedony, a form of silica. However, agate?s layers are formed over geological time, which is considerably different from the few minutes it takes for the pollen to form its layers. And the details of how the layering happens are different: in agate, it?s not simply a result of fluid flow; instead, it comes from a complicated process involving the interplay of the spreading (diffusion) of mineral ingredients in the fluid from which the mineral forms and crystallizes.

The photo above is a shot of a 5-centimetre sample of the mineral agate. It was imaged at high resolution by a desktop scanner. The patterns are layers of silica.

Page 90 MOMENT I was having dinner at a friend?s house. She's a terrific cook, and she insisted that the best pots are made of copper. I am not sure I agree with her, but when I helped wash the pots, I was drawn to the stunning colors at the bottom of one of her pots. I asked if I could borrow it, and I brought it to my studio. With daylight from my window, I made the image with my DSLR camera. PHENOMENON When copper is exposed to heat and air, it undergoes oxidation (similar to what we saw on pages 76?77 with the rust on the metal fence), leading to the formation of a thin layer of copper compounds ?especially copper carbonate?on its surface. We call the process patina formation (or just patination). Over time, different types of oxidation reactions take place, forming various copper compounds. The different compounds produce the colors.

Frankel was drawn to the colours in a copper pan in the image above. When copper is exposed to heat and air, it oxidises and forms copper compounds of striking colours.

Page 28 MOMENT I saw this while walking past a driveway after a rainfall and had to think for a moment about what phenomenon I was seeing. I finally recognized where these amazing colors were coming from. PHENOMENON Oil dripping from a car can create a very thin layer (film) on top of the water, creating small puddles of the two. The oil and water don?t mix, meaning they are immiscible. The oil layer has a top and bottom surface. Light waves (composed of all colors, with each color having a different wavelength) can reflect off either the top or bottom surface of the film. Whether a particular color (wavelength) constructively interferes or destructively interferes (cancels itself out) with another wavelength depends on the thickness of the film. Because different parts of the small puddles have different thicknesses, we see the various colors in that region undergoing constructive interference.

Oil dripping from a car created a thin layer on top of a puddle in the final image, above. Light reflects from the top and bottom of the oil layer, which varies in thickness. These reflections create wavelengths in varied colours.

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