RAINBOWS Written by Peg Zenko with Special Edit by Les Cowley
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Diffractive Properties of Blue Morpho Butterfly Wings
Diffractive Properties of Blue Morpho Butterfly Wings Mary Lalak and Paul Brackman Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (Dated: October 24, 2014) Many species of butterflies are known to produce beautiful iridescent colors when exposed to light from different angles. These affects can be attributed to a few different optical phenomena combined, the most prominent being reflective diffraction. Using common household items and with a budget of 50 dollars, we attempt to confirm the theory that the collection of ridges on the individual scales on the wing act as transmission gratings, as well as reflective. These results are quantified by the calculation of the ridge separation and comparing this distance to those observed by a scanning electron microscope photo. I. INTRODUCTION In studying the optical property of iridescence, three distinct mechanisms must be discussed. Thin film inter- ference, structured coloring, and reflective diffraction all contribute to the iridescent qualities of a surface. Thin film interference occurs when light strikes a film, some of it enters the film, and the rest is reflected off. The light transmitted through reflects off the bottom of the film and exits the film to interfere with the light that FIG. 1: Up-Close View of Scales from an Optical Microscope originally reflected off the surface of the film. This inter- ference pattern causes a spectrum of color to be visible from white light. Examples of thin film interference in- clude oil slicks and soap bubbles. Structural coloring oc- curs when the structure of the object itself (with various reflective surfaces) produces an interference resulting in vibrant colors. -
Atmospheric Effects Are Looking Up
Atmospheric Effects are Looking Up OASI Workshop 21st May 2018 by Olaf Kirchner Ever seen one of these ? OK, so how about one of these? Atmospheric Effects - caused by sun- or moonlight interacting with liquid water or ice in the air - surprisingly common - always beautiful and one or several phenomena may be seen at the same time - can be in-your-face obvious or very subtle, and ... - ... span the entire sky - a challenge to photograph - very complicated theoretical explanations Effects caused by Liquid Water Droplets - rainbows - glories, Heiligenschein and the Spectre of the Brocken - aureoles / coronae - nacreous / iridescent / Mother-of-Pearl clouds Rainbow Rainbow Ray paths for primary rainbow Ray paths through a spherical water drop Ray paths for secondary rainbow Secondary Rainbow Secondary rainbow Alexander’s Band Supernumerary rainbow Primary rainbow Rainbow Gap in cloud behind observer = partial rainbow Rainbow in spray, Geneva Jet d’Eau Supernumerary Rainbow Interference colours from different lengths of light path Rainbow Circular rainbow seen from an aircraft Rainbows don’t reflect ... Glory Colourful diffraction rings centred on the antisolar point, caused by reflection from spherical droplets Glory ... i.e. centred on where the shadow of your head would be! Brockengespenst = Spectre of the Brocken Taken against fog from Golden Gate Bridge Brocken (1142 m) . Highest point in the Harz mountains Heiligenschein = Halo Antisolar point in hydrothermal steam ... scary stuff Heiligenschein ... i.e. a glory centred on your head -
Iridescence in Cooked Venison – an Optical Phenomenon
Journal of Nutritional Health & Food Engineering Research Article Open Access Iridescence in cooked venison – an optical phenomenon Abstract Volume 8 Issue 2 - 2018 Iridescence in single myofibers from roast venison resembled multilayer interference in having multiple spectral peaks that were easily visible under water. The relationship HJ Swatland of iridescence to light scattering in roast venison was explored using the weighted- University of Guelph, Canada ordinate method of colorimetry. In iridescent myofibers, a reflectance ratio (400/700 nm) showing wavelength-dependent light scattering was correlated with HJ Swatland, Designation Professor CIE (Commission International de l’Éclairage) Y%, a measure of overall paleness Correspondence: Emeritus, University of Guelph, 33 Robinson Ave, Guelph, (r=0.48, P< 0.01). Hence, meat iridescence is an optical phenomenon. The underlying Ontario N1H 2Y8, Canada, Tel 519-821-7513, mechanism, subsurface multilayer interference, may be important for meat colorimetry. Email [email protected] venison, iridescence, interference, reflectance, meat color Keywords: Received: August 23, 2017 | Published: March 14, 2018 Introduction balanced pixel hues that have tricked your eyes to appear white; and when we perceive interference colors, complex interference spectra Iridescence is an enigmatic aspect of meat color with some practical trick our eyes again. As the order of interference increases, the colors 1–4 importance for consumers concerned about green colors in meat. appear to change from metallic -
Atmospheric Phenomena by Feist
Atmospheric optical phenomena An introductory guide by Mike Feist Effects caused by water droplets— rainbows and coronae The most well known optical sky effect is the rainbow. This, as most people know, sometimes occurs when the Sun is out and it is raining. To see a rainbow you must stand with your back to the Sun with the raindrops in front of you. It does not have to be raining where you are standing but in the direction that you are looking. The arc of the primary (main) bow is centred on the antisolar point, the spot directly oppo- site the Sun, and has a radius of 42°. The antisolar point is actually centred on the shadow of your head. If the Sun is rising or setting and therefore on the horizon, the primary rainbow will be a complete semi- circle and the top will be 42° up in the sky. If, on the other hand, the Sun is 42° up in the sky, the primary bow will be on the horizon, the top just rising or setting. Con- ventionally the rainbow is said to have John Constable. Hampstead Heath with a Rainbow (1836). seven colours but all we need to remember seen in the spray near waterfalls and artifi- ous forms but with a six-sided shape. They is that, in the primary bow, the red is on cial rainbows can be made using a garden may be as flat hexagonal plates or long the outside and the blue on the inside. Out- hose. Rainbows are one of the easiest opti- hexagonal prisms or as a combination of side the primary bow sometimes there is cal effects to photograph although they the two. -
Octopus Consciousness: the Role of Perceptual Richness
Review Octopus Consciousness: The Role of Perceptual Richness Jennifer Mather Department of Psychology, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada; [email protected] Abstract: It is always difficult to even advance possible dimensions of consciousness, but Birch et al., 2020 have suggested four possible dimensions and this review discusses the first, perceptual richness, with relation to octopuses. They advance acuity, bandwidth, and categorization power as possible components. It is first necessary to realize that sensory richness does not automatically lead to perceptual richness and this capacity may not be accessed by consciousness. Octopuses do not discriminate light wavelength frequency (color) but rather its plane of polarization, a dimension that we do not understand. Their eyes are laterally placed on the head, leading to monocular vision and head movements that give a sequential rather than simultaneous view of items, possibly consciously planned. Details of control of the rich sensorimotor system of the arms, with 3/5 of the neurons of the nervous system, may normally not be accessed to the brain and thus to consciousness. The chromatophore-based skin appearance system is likely open loop, and not available to the octopus’ vision. Conversely, in a laboratory situation that is not ecologically valid for the octopus, learning about shapes and extents of visual figures was extensive and flexible, likely consciously planned. Similarly, octopuses’ local place in and navigation around space can be guided by light polarization plane and visual landmark location and is learned and monitored. The complex array of chemical cues delivered by water and on surfaces does not fit neatly into the components above and has barely been tested but might easily be described as perceptually rich. -
ESSENTIALS of METEOROLOGY (7Th Ed.) GLOSSARY
ESSENTIALS OF METEOROLOGY (7th ed.) GLOSSARY Chapter 1 Aerosols Tiny suspended solid particles (dust, smoke, etc.) or liquid droplets that enter the atmosphere from either natural or human (anthropogenic) sources, such as the burning of fossil fuels. Sulfur-containing fossil fuels, such as coal, produce sulfate aerosols. Air density The ratio of the mass of a substance to the volume occupied by it. Air density is usually expressed as g/cm3 or kg/m3. Also See Density. Air pressure The pressure exerted by the mass of air above a given point, usually expressed in millibars (mb), inches of (atmospheric mercury (Hg) or in hectopascals (hPa). pressure) Atmosphere The envelope of gases that surround a planet and are held to it by the planet's gravitational attraction. The earth's atmosphere is mainly nitrogen and oxygen. Carbon dioxide (CO2) A colorless, odorless gas whose concentration is about 0.039 percent (390 ppm) in a volume of air near sea level. It is a selective absorber of infrared radiation and, consequently, it is important in the earth's atmospheric greenhouse effect. Solid CO2 is called dry ice. Climate The accumulation of daily and seasonal weather events over a long period of time. Front The transition zone between two distinct air masses. Hurricane A tropical cyclone having winds in excess of 64 knots (74 mi/hr). Ionosphere An electrified region of the upper atmosphere where fairly large concentrations of ions and free electrons exist. Lapse rate The rate at which an atmospheric variable (usually temperature) decreases with height. (See Environmental lapse rate.) Mesosphere The atmospheric layer between the stratosphere and the thermosphere. -
Atmospheric Optics
53 Atmospheric Optics Craig F. Bohren Pennsylvania State University, Department of Meteorology, University Park, Pennsylvania, USA Phone: (814) 466-6264; Fax: (814) 865-3663; e-mail: [email protected] Abstract Colors of the sky and colored displays in the sky are mostly a consequence of selective scattering by molecules or particles, absorption usually being irrelevant. Molecular scattering selective by wavelength – incident sunlight of some wavelengths being scattered more than others – but the same in any direction at all wavelengths gives rise to the blue of the sky and the red of sunsets and sunrises. Scattering by particles selective by direction – different in different directions at a given wavelength – gives rise to rainbows, coronas, iridescent clouds, the glory, sun dogs, halos, and other ice-crystal displays. The size distribution of these particles and their shapes determine what is observed, water droplets and ice crystals, for example, resulting in distinct displays. To understand the variation and color and brightness of the sky as well as the brightness of clouds requires coming to grips with multiple scattering: scatterers in an ensemble are illuminated by incident sunlight and by the scattered light from each other. The optical properties of an ensemble are not necessarily those of its individual members. Mirages are a consequence of the spatial variation of coherent scattering (refraction) by air molecules, whereas the green flash owes its existence to both coherent scattering by molecules and incoherent scattering -
The Quest for the Gegenschein Erwin Matys, Karoline Mrazek
The Quest for the Gegenschein Erwin Matys, Karoline Mrazek The sun’s counterglow — or gegenschein — is kind of a stargazers’ legend. Every amateur astronomer has heard about it, only a few of them have actually seen it, and even fewer were lucky enough to capture an image of this dim and ghostlike apparition. As a fellow observer put it: “The gegenschein is certainly not a GOTO-object.” Matter of fact, it isn’t an object at all. But let’s start from the beginning. What exactly is the gegenschein? It is widely known that the space between the planets isn’t empty. The plane of the solar system is filled with an enormous disk of small dust particles with sizes ranging from less than 1/1000 mm up to 1 mm. It is less commonly known that this interplanetary dust cloud is a highly dynamic structure. In contrast to conventional wisdom, it is not an aeon-old leftover from the solar system’s formation. This primordial dust is long gone. Today’s interplanetary dust is — in an astronomical sense of speaking — very young, only millions of years old. Most of the particles originate from quite recent incidents, like asteroid collisions. This is not the gegenschein. The picture shows the zodiacal light, which is closely related to the gegenschein. Here imaged from a rural site, the zodiacal light is a cone of light extending from the sun along the ecliptic, visible after dusk and before dawn. The gegenschein stems from the same dust cloud, but is much harder to detect or photograph. -
Wfc3 Isr 2014
SPACE TELESCOPE SCIENCE INSTITUTE Operated for NASA by AURA Instrument Science Report WFC3 2014-11 The Near Infrared Sky Background N. Pirzkal May 13, 2014 ABSTRACT WFC3 IR observations are often background limited. In the vast majority of cases, when HST is pointed away from the Earth Limb, the main contribution to this background light is caused by zodiacal infrared light, including the Gegenschein, the diffuse glow in the sky centered upon Earth's antisolar point. In this ISR, we present direct measurements of the infrared background levels as observed by WFC3 since its launch and in several broad band filters. We compare our observations to the values currently used in the Exposure Time Calculator (ETC) and derive a model of the IR background levels as a function of Ecliptic Latitude and Sun Angle. Data and Analysis WFC3 IR images have been continuously monitored since the installation of WFC3 on board of HST, as part of the \Blob" Monitoring Program (Pirzkal et al. 2012) and the making of deep sky-flats (Pirzkal et al. 2011). The data that were used and details of the procedures used are given in Pirzkal et al. 2011 and Pirzkal et al. 2012. As part of this routine monitoring, we naturally needed to accurately measure the background level in each of the available infrared exposures. The was done by first generating an object mask using SExtractor for each individual FLT file. This mask was then used to mask out sources in each of the IMSET of the original IMA file and we then computed the background in each IMSET Copyright c 2008 The Association of Universities for Research in Astronomy, Inc. -
Atmospheric Optical Phenomena and Radiative Transfer
ATMOSPHERIC OPTICAL PHENOMENA AND RADIATIVE TRANSFER BY STANLEY DAVID GEDZELMAN AND MICHAEL VOLLMER Sky colors, rainbows, and halos are simulated using models that include light scattered as it passes through clear air and clouds of finite optical depth. ivid rainbows, ice crystal halos, coronas, iridescence, glories, mirages, sky colors, and crepuscular rays have Valways inspired awe and wonder. This makes simulating atmospheric optical phenomena both a scientific and aesthetic undertaking. Atmospheric optics has a venerable history (Pernter and Exner 1922; Minnaert 1993; Humphreys 1940; Tricker 1970; Greenler 1980; Meinel and Meinel 1983; Lynch and Livingston 2001), because the phenomena appear so simple and striking, and because scientists emphasized this branch of atmospheric science at a time when it was far more difficult to examine large-scale weather systems. Discoveries made about or involving the rainbow by Rene Descartes, Isaac Newton, and Thomas Young rank among the early triumphs of the scientific revolution (Boyer 1987). All optical phenomena are produced when air molecules, aerosol particles, or hydrometeors either scatter or absorb light as it passes through the atmosphere. Many of the observed features of the optical phenomena can be reproduced by applying a scattering theory of light to a single particle. This can be done at various levels of complexity. The most accurate and perhaps most intricate Rainbow. " University Corporation for Atmospheric theories involve • i Research, Photo by Carlye Calvin BAH5- AMERICAN METEOROLOGICAL SOCIETY Unauthenticated | DownloadedAPRIL 2008 10/09/21 01:28 AM UTC solving Maxwell's equations with appropriate bound- flattening of drops (Fraser 1983), while models of ary conditions. -
Rainbow Peacock Spiders Inspire Miniature Super-Iridescent Optics
ARTICLE DOI: 10.1038/s41467-017-02451-x OPEN Rainbow peacock spiders inspire miniature super- iridescent optics Bor-Kai Hsiung 1,8, Radwanul Hasan Siddique 2, Doekele G. Stavenga 3, Jürgen C. Otto4, Michael C. Allen5, Ying Liu6, Yong-Feng Lu 6, Dimitri D. Deheyn 5, Matthew D. Shawkey 1,7 & Todd A. Blackledge1 Colour produced by wavelength-dependent light scattering is a key component of visual communication in nature and acts particularly strongly in visual signalling by structurally- 1234567890 coloured animals during courtship. Two miniature peacock spiders (Maratus robinsoni and M. chrysomelas) court females using tiny structured scales (~ 40 × 10 μm2) that reflect the full visual spectrum. Using TEM and optical modelling, we show that the spiders’ scales have 2D nanogratings on microscale 3D convex surfaces with at least twice the resolving power of a conventional 2D diffraction grating of the same period. Whereas the long optical path lengths required for light-dispersive components to resolve individual wavelengths constrain current spectrometers to bulky sizes, our nano-3D printed prototypes demonstrate that the design principle of the peacock spiders’ scales could inspire novel, miniature light-dispersive components. 1 Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325, USA. 2 Department of Medical Engineering, California Institute of Technology, Pasadena, CA 91125, USA. 3 Department of Computational Physics, University of Groningen, 9747 AG Groningen, The Netherlands. 4 19 Grevillea Avenue, St. Ives, NSW 2075, Australia. 5 Scripps Institution of Oceanography (SIO), University of California, San Diego, La Jolla, CA 92093, USA. 6 Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA. -
Table Talk Succos VOLUME FOUR.Pub
MADE POSSIBLE IN ABLE ALK PART THROUGH A T T GRANT FROM THE STAR-K VAAD OCTOBER 2020 SUCCOS WWW.ACHIM.ORG ISSUE 201 VOLUME 4 HAKASHRUS A MITZVA DILEMMA FOR THE SHABBOS TABLE BALCONY SUCCAH MUSCLE BUILDING We know that everything that happens to us comes from HaShem. When everything in life By Rabbi Yitzi Weiner runs smoothly we ‘understand’ why everything is smooth. However, when life becomes complicated we struggle to understand why HaShem changed His plan. How are we to make sense out of circumstances when they go totally out of control. This question sits on This week is the holiday of Succos. We my mind as we all find ourselves in the middle of Covid and life has spun out of control. all know that on Succos there is a mitz- Although we have no Navi to direct us to the answer, nevertheless, there are clues to vah to live and sleep in a succah in order which we must pay attention. to remember the clouds of glory that pro- Let us leave Covid for a moment and enter the life of a young couple that just had their tected the Jewish people during their trav- third child. Sibling rivalry begins to lift its head and the parents struggle to keep the home els in the desert. This leads us to the fol- peaceful. Nobody is at fault for this challenge; that is how children are programmed. As lowing story. the parents work their way through this challenge, they discover that when they practice Akiva and his family lived in an apart- patience the situation becomes more manageable.