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• Course web page: – Contains important information about the course. – Course Introduction. • Reference Textbook: – Computer Science Illuminated, 3rd ed. Nell Dale & John Lewis. Jones and Bartlett, pub. ISBN 0-7637-4149-3. Companion Website. Sep 20, 2013. N E L L D A L E J O H N L E W I S J O N E S A N D B A R T L E T T C O M P U T E R S C I E N C E c o m p u t e r s c i e n c e illuminated. These high-level languages allowed the 20 Chapter 1 The Big Picture Third-Generation Software (1965–1971) During 1.2 The History of Computing 21 Assembly.

This textbook automatically ships with an Access Code to Navigate 2 bound-in. Stand alone Access Codes to Navigate 2 can be purchased at 50% off the list price of the textbook. Price: $204.95 US List • •. The Essentials of Computer Organization and Architecture, Fourth Edition was recently awarded a (“Texty”) from the the only association devoted solely to serving textbook and academic authors since 1987 (www.TAAonline.net). The 'Textbook Excellence Award' recognizes works for their excellence in the areas of content, presentation, appeal, and teachability. This is the third Texty award for Null and Lobur. They also won for their Second and Third Editions of this text.

Each new print copy of Essentials of Computer Organization and Architecture also includes Navigate 2 Advantage Access that unlocks a comprehensive and interactive eBook, student practice activities and assessments, a full suite of instructor resources, and learning analytics reporting tools. Updated and revised to reflect the most current data in the field, perennial bestseller The Essentials of Computer Organization and Architecture, Fourth Edition is comprehensive enough to address all necessary organization and architecture topics, but concise enough to be appropriate for a single-term course. Its focus on real-world examples and practical applications encourages students to develop a “big-picture” understanding of how essential organization and architecture concepts are applied in the computing world. In addition to direct correlation with the ACM/IEEE CS2013 guidelines for computer organization and architecture, the text exposes readers to the inner workings of a modern digital computer through an integrated presentation of fundamental concepts and principles.

The fully revised and updated Fourth Edition includes the most up-to-the-minute data and resources available and reflects current technologies, including tablets and cloud computing. All-new exercises, expanded discussions, and feature boxes in every chapter implement even more real-world applications and current data, and many chapters include all-new examples. A full suite of student and instructor resources, including a secure companion website, Lecture Outlines in PowerPoint Format, and an Instructor Manual complement the text. This award-winning, best-selling text is the most thorough, student-friendly, and accessible text on the market today.

With Navigate 2, technology and content combine to expand the reach of your classroom. Whether you teach an online, hybrid, or traditional classroom-based course, Navigate 2 delivers unbeatable value. Experience Navigate 2 today. Features & Benefits • The Fourth Edition is in direct correlation with the ACM/IEEE CS2013 guidelines for computer organization and architecture, in addition to integrating material from additional knowledge units. • All-new material on a variety of topics, including zetabytes and yottabytes, automatons, tablet computers, graphic processing units, and cloud computing • The MARIE Simulator package allows students to learn the essential concepts of computer organization and architecture, including assembly language, without getting caught up in unnecessary and confusing details. • Full suite of ancillary materials, including a secure companion website, Lecture Outlines in PowerPoint Format, an all-new Test Bank, and an Instructor Manual • Bundled with an optional Intel supplement • Ideally suited for single-term courses. Chapter 1 Introduction Chapter 2 Data Representation in Computer Systems Chapter 3 Boolean Algebra and Digital Logic Chapter 4 MARIE: An Introduction to a Simple Computer Chapter 5 A Closer Look at Instruction Set Architecture Chapter 6 Memory Chapter 7 Input/Output and Storage Systems Chapter 8 System Software Chapter 9 Alternative Architectures Chapter 10 Topics in Embedded Systems Chapter 11 Performance Measurement and Analysis Chapter 12 Network Organization and Architecture Chapter 13 Selected Storage Systems and Interfaces Appendix A Data Structures and the Computer.

Linda Null, PhD-Pennsylvania State University Linda Null received a Ph.D. In Computer Science from Iowa State University in 1991, an M.S. In Computer Science from Iowa State University in 1989, an M.S.

In Computer Science Education from Northwest Missouri State University in 1983, an M.S. In Mathematics Education from Northwest Missouri State University in 1980, and a B.S. In Mathematics and English from Northwest Missouri State University in 1977. She has been teaching mathematics and computer science for over 25 years and is currently the Computer Science graduate program coordinator at Penn State Harrisburg, where she has been a member of the faculty since 1995. Professor Null was recently presented Penn State's Award for Excellence in Teaching in recognition of her innovative and outstanding work in the classroom, as well as the Kathryn Towns Award in recognition of her commitment to the issues and interests of women students, particularly those in mathematics and computer science.

Her areas of interest include computer organization and architecture, operating systems, and computer security. • “ Essentials of Computer Organization and Architecture is an outstanding text that builds from the lowest level of logic gates through the circuits of the CPU up to the complexity of modern machines. I’ve used this text since 2008 (Second Edition). Each new edition has brought additional clarity to the material. One of my students said, at the end of the term, “I feel like I could build a computer from scratch!” The exercises are well-designed so that I can assign problems that test the topics we’ve focused on. It is a vast, rich collection of information.” Jacqueline A. Jones Associate Professor, Dept.

Of Computer and Information Science Brooklyn College of the City University of New York. MARIEsimulator version 3.0 ISBN-13: Download all the files you need to assemble and run MARIE programs. For more information about the MARIE architecture please consult your textbook. Enclosed in this zip file are: 1. MarieSim.jar (java jar file for the simulator) 2. MarieSource.jar (the source file for the simulator) 3. README.txt 4.

MarieGuide.doc (a user's guide in WORD format) 5. MarieGuide.pdf (a user’s guide in PDF format) Version 3.0 is now available. Please check back periodically to ensure that you are using the latest version. Download the MARIEsimulator version 3.0 under the Samples & Additional Resources tab above. $19.95 An Introduction to MIPS Assembly Language to Accompany The Essentials of Computer Organization and Architecture ISBN-13: 936 An Introduction to MIPS Assembly Language.

Double rainbow and supernumerary rainbows on the inside of the primary arc. The shadow of the photographer's head on the bottom marks the centre of the rainbow circle ().

A rainbow is a phenomenon that is caused by, and of light in water droplets resulting in a of light appearing in the sky. It takes the form of a multicoloured circular.

Rainbows caused by sunlight always appear in the section of sky directly opposite the sun. Rainbows can be full circles. However, the observer normally sees only an arc formed by illuminated droplets above the ground, and centered on a line from the sun to the observer's eye. In a primary rainbow, the arc shows red on the outer part and violet on the inner side.

This rainbow is caused by light being when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it. In a double rainbow, a second arc is seen outside the primary arc, and has the order of its colors reversed, with red on the inner side of the arc. This is caused by the light being reflected twice on the inside of the droplet before leaving it. Image of the end of a rainbow at A rainbow is not located at a specific distance from the observer, but comes from an optical illusion caused by any water droplets viewed from a certain angle relative to a light source. Thus, a rainbow is not an object and cannot be physically approached.

Indeed, it is impossible for an observer to see a rainbow from water droplets at any angle other than the customary one of 42 degrees from the direction opposite the light source. Even if an observer sees another observer who seems 'under' or 'at the end of' a rainbow, the second observer will see a different rainbow—farther off—at the same angle as seen by the first observer. Rainbows span a continuous spectrum of colours. Any distinct bands perceived are an artefact of human, and no banding of any type is seen in a black-and-white photo of a rainbow, only a smooth gradation of intensity to a maximum, then fading towards the other side. For colours seen by the human eye, the most commonly cited and remembered sequence is 's sevenfold red, orange, yellow, green, blue, and violet, remembered by the, Richard Of York Gave Battle In Vain (). Rainbows can be caused by many forms of airborne water.

How To Install Slax Linux. These include not only rain, but also mist, spray, and airborne. Rainbows may form in the spray created by waves (called spray bows). Rainbows can be observed whenever there are water drops in the air and sunlight shining from behind the observer at a low. Because of this, rainbows are usually seen in the western sky during the morning and in the eastern sky during the early evening. The most spectacular rainbow displays happen when half the sky is still dark with raining and the observer is at a spot with clear sky in the direction of the sun. The result is a luminous rainbow that contrasts with the darkened background.

During such good visibility conditions, the larger but fainter secondary rainbow is often visible. It appears about 10° outside of the primary rainbow, with inverse order of colours. The rainbow effect is also commonly seen near waterfalls or fountains. In addition, the effect can be artificially created by dispersing water droplets into the air during a sunny day. Rarely, a, lunar rainbow or nighttime rainbow, can be seen on strongly moonlit nights. As human for colour is poor in low light, moonbows are often perceived to be white.

It is difficult to photograph the complete semicircle of a rainbow in one frame, as this would require an of 84°. For a camera, a with a of 19 mm or less would be required. Now that software for several images into a is available, images of the entire arc and even secondary arcs can be created fairly easily from a series of overlapping frames. From above the earth such as in an aeroplane, it is sometimes possible to see a rainbow as a full circle. This phenomenon can be confused with the phenomenon, but a glory is usually much smaller, covering only 5–20°. The sky inside a primary rainbow is brighter than the sky outside of the bow. This is because each raindrop is a sphere and it scatters light over an entire circular disc in the sky.

The radius of the disc depends on the wavelength of light, with red light being scattered over a larger angle than blue light. Over most of the disc, scattered light at all wavelengths overlaps, resulting in white light which brightens the sky. At the edge, the wavelength dependence of the scattering gives rise to the rainbow. Light of primary rainbow arc is 96% tangential to the arch. Light of second arc is 90% polarised. Number of colours in spectrum or rainbow A obtained using a glass prism and a point source is a continuum of wavelengths without bands.

The number of colours that the human eye is able to distinguish in a spectrum is in the order of 100. Accordingly, the (a 20th-century system for numerically describing colours, based on equal steps for human visual perception) distinguishes 100 hues.

The apparent discreteness of main colours is an artefact of human perception and the exact number of main colours is a somewhat arbitrary choice. Newton, who admitted his eyes were not very critical in distinguishing colours, originally (1672) divided the spectrum into five main colours: red, yellow, green, blue and violet. Later he included orange and indigo, giving seven main colours by analogy to the number of notes in a musical scale.

Newton chose to divide the visible spectrum into seven colours out of a belief derived from the beliefs of the, who thought there was a connection between the colours, the musical notes, the known objects in the Solar System, and the days of the week. Rainbow (middle: real, bottom: computed) compared to true spectrum (top): unsaturated colours and different colour profile According to, 'It is customary to list indigo as a color lying between blue and violet, but it has never seemed to me that indigo is worth the dignity of being considered a separate color. To my eyes it seems merely deep blue.'

The colour pattern of a rainbow is different from a spectrum, and the colours are less saturated. There is spectral smearing in a rainbow owing to the fact that for any particular wavelength, there is a distribution of exit angles, rather than a single unvarying angle. In addition, a rainbow is a blurred version of the bow obtained from a point source, because the disk diameter of the sun (0.5°) cannot be neglected compared to the width of a rainbow (2°). The number of colour bands of a rainbow may therefore be different from the number of bands in a spectrum, especially if the droplets are particularly large or small. Therefore, the number of colours of a rainbow is variable. If, however, the word rainbow is used inaccurately to mean spectrum, it is the number of main colours in the spectrum. The question of whether everyone sees seven colours in a rainbow is related to the idea of.

Suggestions have been made that there is universality in the way that a rainbow is perceived. However, more recent research suggests that the number of distinct colours observed and what these are called depend on the language that one uses with people whose language has fewer colour words seeing fewer discrete colour bands. White light separates into different colours on entering the raindrop due to dispersion, causing red light to be refracted less than blue light. When sunlight encounters a raindrop, part of the light is reflected and the rest enters the raindrop. The light is at the surface of the raindrop. When this light hits the back of the raindrop, some of it is reflected off the back. When the internally reflected light reaches the surface again, once more some is internally reflected and some is refracted as it exits the drop.

(The light that reflects off the drop, exits from the back, or continues to bounce around inside the drop after the second encounter with the surface, is not relevant to the formation of the primary rainbow.) The overall effect is that part of the incoming light is reflected back over the range of 0° to 42°, with the most intense light at 42°. This angle is independent of the size of the drop, but does depend on its. Seawater has a higher refractive index than rain water, so the radius of a 'rainbow' in sea spray is smaller than a true rainbow.

This is visible to the naked eye by a misalignment of these bows. The reason the returning light is most intense at about 42° is that this is a turning point – light hitting the outermost ring of the drop gets returned at less than 42°, as does the light hitting the drop nearer to its centre. There is a circular band of light that all gets returned right around 42°. If the sun were a laser emitting parallel, monochromatic rays, then the (brightness) of the bow would tend toward infinity at this angle (ignoring interference effects). (See.) But since the sun's luminance is finite and its rays are not all parallel (it covers about half a degree of the sky) the luminance does not go to infinity. Furthermore, the amount by which light is refracted depends upon its, and hence its colour.

This effect is called. Blue light (shorter wavelength) is refracted at a greater angle than red light, but due to the reflection of light rays from the back of the droplet, the blue light emerges from the droplet at a smaller angle to the original incident white light ray than the red light. Due to this angle, blue is seen on the inside of the arc of the primary rainbow, and red on the outside. The result of this is not only to give different colours to different parts of the rainbow, but also to diminish the brightness. (A 'rainbow' formed by droplets of a liquid with no dispersion would be white, but brighter than a normal rainbow.) The light at the back of the raindrop does not undergo, and some light does emerge from the back. However, light coming out the back of the raindrop does not create a rainbow between the observer and the sun because spectra emitted from the back of the raindrop do not have a maximum of intensity, as the other visible rainbows do, and thus the colours blend together rather than forming a rainbow. A rainbow does not exist at one particular location.

Many rainbows exist; however, only one can be seen depending on the particular observer's viewpoint as droplets of light illuminated by the sun. All raindrops refract and reflect the sunlight in the same way, but only the light from some raindrops reaches the observer's eye. This light is what constitutes the rainbow for that observer. The whole system composed by the sun's rays, the observer's head, and the (spherical) water drops has an around the axis through the observer's head and parallel to the sun's rays. The rainbow is curved because the set of all the raindrops that have the right angle between the observer, the drop, and the sun, lie on a pointing at the sun with the observer at the tip. The base of the cone forms a circle at an angle of 40–42° to the line between the observer's head and their shadow but 50% or more of the circle is below the horizon, unless the observer is sufficiently far above the earth's surface to see it all, for example in an aeroplane (see above). Alternatively, an observer with the right vantage point may see the full circle in a fountain or waterfall spray.

Mathematical derivation. Double rainbow created in the mist of Secondary rainbows are caused by a double reflection of sunlight inside the raindrops, and are centred on the sun itself. They are about 127° (violet) to 130° (red) wide. Since this is more than 90°, they are seen on the same side of the sky as the primary rainbow, about 10° above it at apparent angles of 50–53°. As a result of the 'inside' of the secondary bow being 'up' to the observer, the colours appear reversed compared to the primary bow. The secondary rainbow is fainter than the primary because more light escapes from two reflections compared to one and because the rainbow itself is spread over a greater area of the sky. Each rainbow reflects white light inside its coloured bands, but that is 'down' for the primary and 'up' for the secondary.

The dark area of unlit sky lying between the primary and secondary bows is called, after who first described it. Twinned rainbow Unlike a double rainbow that consists of two separate and concentric rainbow arcs, the very rare twinned rainbow appears as two rainbow arcs that split from a single base. The colours in the second bow, rather than reversing as in a secondary rainbow, appear in the same order as the primary rainbow.

A 'normal' secondary rainbow may be present as well. Twinned rainbows can look similar to, but should not be confused with. The two phenomena may be told apart by their difference in colour profile: supernumerary bands consist of subdued pastel hues (mainly pink, purple and green), while the twinned rainbow shows the same spectrum as a regular rainbow. The cause of a twinned rainbow is the combination of different sizes of water drops falling from the sky.

Due to air resistance, raindrops flatten as they fall, and flattening is more prominent in larger water drops. When two rain showers with different-sized raindrops combine, they each produce slightly different rainbows which may combine and form a twinned rainbow.

A numerical ray tracing study showed that a twinned rainbow on a photo could be explained by a mixture of 0.40 and 0.45 mm droplets. That small difference in droplet size resulted in a small difference in flattening of the droplet shape, and a large difference in flattening of the rainbow top. Circular rainbow Meanwhile, the even rarer case of a rainbow split into three branches was observed and photographed in nature. Full-circle rainbow In theory, every rainbow is a circle, but from the ground, only its upper half can be seen.

Since the rainbow's centre is diametrically opposed to the sun's position in the sky, more of the circle comes into view as the sun approaches the horizon, meaning that the largest section of the circle normally seen is about 50% during sunset or sunrise. Viewing the rainbow's lower half requires the presence of water droplets below the observer's horizon, as well as sunlight that is able to reach them. These requirements are not usually met when the viewer is at ground level, either because droplets are absent in the required position, or because the sunlight is obstructed by the landscape behind the observer. From a high viewpoint such as a high building or an aircraft, however, the requirements can be met and the full-circle rainbow can be seen.

Like a partial rainbow, the circular rainbow can have a or as well. It is possible to produce the full circle when standing on the ground, for example by spraying a water mist from a garden hose while facing away from the sun. A circular rainbow should not be confused with the, which is much smaller in diameter and is created by different optical processes. In the right circumstances, a glory and a (circular) rainbow or can occur together. Another atmospheric phenomenon that may be mistaken for a 'circular rainbow' is the, which is caused by rather than liquid water droplets, and is located around the sun (or moon), not opposite it.

Supernumerary rainbows. Contrast-enhanced photograph of a rainbow with additional supernumerary bands inside the primary bow In certain circumstances, one or several narrow, faintly coloured bands can be seen bordering the violet edge of a rainbow; i.e., inside the primary bow or, much more rarely, outside the secondary. These extra bands are called supernumerary rainbows or supernumerary bands; together with the rainbow itself the phenomenon is also known as a stacker rainbow.

The supernumerary bows are slightly detached from the main bow, become successively fainter along with their distance from it, and have pastel colours (consisting mainly of pink, purple and green hues) rather than the usual spectrum pattern. The effect becomes apparent when water droplets are involved that have a diameter of about 1 mm or less; the smaller the droplets are, the broader the supernumerary bands become, and the less saturated their colours. Due to their origin in small droplets, supernumerary bands tend to be particularly prominent in. Supernumerary rainbows cannot be explained using classical geometric. The alternating faint bands are caused by between rays of light following slightly different paths with slightly varying lengths within the raindrops.

Some rays are in, reinforcing each other through, creating a bright band; others are out of phase by up to half a wavelength, cancelling each other out through, and creating a gap. Given the different angles of refraction for rays of different colours, the patterns of interference are slightly different for rays of different colours, so each bright band is differentiated in colour, creating a miniature rainbow. Supernumerary rainbows are clearest when raindrops are small and of uniform size. The very existence of supernumerary rainbows was historically a first indication of the nature of light, and the first explanation was provided by in 1804. Reflected rainbow, reflection rainbow.

Reflection rainbow (top) and normal rainbow (bottom) at sunset When a rainbow appears above a body of water, two complementary mirror bows may be seen below and above the horizon, originating from different light paths. Their names are slightly different. A reflected rainbow may appear in the water surface below the horizon. The sunlight is first deflected by the raindrops, and then reflected off the body of water, before reaching the observer. The reflected rainbow is frequently visible, at least partially, even in small puddles. A reflection rainbow may be produced where sunlight reflects off a body of water before reaching the raindrops (see and ), if the water body is large, quiet over its entire surface, and close to the rain curtain.

The reflection rainbow appears above the horizon. It intersects the normal rainbow at the horizon, and its arc reaches higher in the sky, with its centre as high above the horizon as the normal rainbow's centre is below it. Due to the combination of requirements, a reflection rainbow is rarely visible. Up to eight separate bows may be distinguished if the reflected and reflection rainbows happen to occur simultaneously: The normal (non-reflection) primary and secondary bows above the horizon (1, 2) with their reflected counterparts below it (3, 4), and the reflection primary and secondary bows above the horizon (5, 6) with their reflected counterparts below it (7, 8). Monochrome rainbow. Unenhanced photo of a red (monochrome) rainbow Occasionally a shower may happen at sunrise or sunset, where the shorter wavelengths like blue and green have been scattered and essentially removed from the spectrum.

Further scattering may occur due to the rain, and the result can be the rare and dramatic monochrome or red rainbow. Higher-order rainbows In addition to the common primary and secondary rainbows, it is also possible for rainbows of higher orders to form. The order of a rainbow is determined by the number of light reflections inside the water droplets that create it: One reflection results in the first-order or primary rainbow; two reflections create the second-order or secondary rainbow. More internal reflections cause bows of higher orders—theoretically unto infinity. As more and more light is lost with each internal reflection, however, each subsequent bow becomes progressively dimmer and therefore increasingly harder to spot.

An additional challenge in observing the third-order (or tertiary) and fourth-order ( quaternary) rainbows is their location in the direction of the sun (about 40° and 45° from the sun, respectively), causing them to become drowned in its glare. For these reasons, naturally occurring rainbows of an order higher than 2 are rarely visible to the naked eye.

Nevertheless, sightings of the third-order bow in nature have been reported, and in 2011 it was photographed definitively for the first time. Shortly after, the fourth-order rainbow was photographed as well, and in 2014 the first ever pictures of the fifth-order (or quinary) rainbow, located in between the primary and secondary bows, were published. In a laboratory setting, it is possible to create bows of much higher orders. Felix Billet (1808–1882) depicted angular positions up to the 19th-order rainbow, a pattern he called a 'rose of rainbows'. In the laboratory, it is possible to observe higher-order rainbows by using extremely bright and well light produced.

Up to the 200th-order rainbow was reported by Ng et al. In 1998 using a similar method but an argon ion laser beam. Tertiary and quaternary rainbows should not be confused with 'triple' and 'quadruple' rainbows—terms sometimes erroneously used to refer to the—much more common—supernumerary bows and reflection rainbows. Main article: Like most atmospheric optical phenomena, rainbows can be caused by light from the Sun, but also from the Moon. In case of the latter, the rainbow is referred to as a lunar rainbow. They are much dimmer and rarer than solar rainbows, requiring the Moon to be near-full in order for them to be seen.

For the same reason, moonbows are often perceived as white and may be thought of as monochrome. The full spectrum is present, however, but the human eye is not normally sensitive enough to see the colours. Long exposure photographs will sometimes show the colour in this type of rainbow.

Main article: Fogbows form in the same way as rainbows, but they are formed by much smaller cloud and fog droplets that diffract light extensively. They are almost white with faint reds on the outside and blues inside; often one or more broad can be discerned inside the inner edge. The colours are dim because the bow in each colour is very broad and the colours overlap. Fogbows are commonly seen over water when air in contact with the cooler water is chilled, but they can be found anywhere if the fog is thin enough for the sun to shine through and the sun is fairly bright. They are very large—almost as big as a rainbow and much broader. They sometimes appear with a at the bow's centre. Fog bows should not be confused with, which are very common around the world and visible much more often than rainbows (of any order), yet are unrelated to rainbows.

Circumhorizontal and circumzenithal arcs. Circumzenithal arc The and are two related optical phenomena similar in appearance to a rainbow, but unlike the latter, their origin lies in light refraction through hexagonal rather than liquid water droplets. This means that they are not rainbows, but members of the large family of. Both arcs are brightly coloured ring segments centred on the, but in different positions in the sky: The circumzenithal arc is notably curved and located high above the Sun (or Moon) with its convex side pointing downwards (creating the impression of an 'upside down rainbow'); the circumhorizontal arc runs much closer to the horizon, is more straight and located at a significant distance below the Sun (or Moon). Both arcs have their red side pointing towards the sun and their violet part away from it, meaning the circumzenithal arc is red on the bottom, while the circumhorizontal arc is red on top. The is sometimes referred to by the misnomer 'fire rainbow'.

In order to view it, the Sun or Moon must be at least 58° above the horizon, making it a rare occurrence at higher latitudes. The circumzenithal arc, visible only at a solar or lunar elevation of less than 32°, is much more common, but often missed since it occurs almost directly overhead. Rainbows on Titan It has been suggested that rainbows might exist on 's moon, as it has a wet surface and humid clouds. The radius of a Titan rainbow would be about 49° instead of 42°, because the fluid in that cold environment is methane instead of water. Although visible rainbows may be rare due to, rainbows may be more common, but an observer would need infrared to see them.

Rainbows with different materials. Round bottom flask rainbow demonstration experiment - Johnson 1882 Experiments on the rainbow phenomenon using artificial raindrops, i.e.

Water-filled spherical flasks, go back at least to in the 14th century. Later, also Descartes studied the phenomenon using a. A flask experiment known as Florence's rainbow is still often used today as an imposing and intuitively accessible demonstration experiment of the rainbow phenomenon. It consists in illuminating (with parallel white light) a water-filled spherical flask through a hole in a screen. A rainbow will then appear thrown back / projected on the screen, provided the screen is large enough. Due to the finite wall thickness and the macroscopic character of the artificial raindrop, several subtle differences exist as compared to the natural phenomenon, including slightly changed rainbow angles and a splitting of the rainbow orders. A very similar experiment consists in using a cylindrical glass vessel filled with water or a solid transparent cylinder and illuminated either parallel to the circular base (i.e.

Light rays remaining at a fixed height while they transit the cylinder) or under an angle to the base. Under these latter conditions the rainbow angles change relative to the natural phenomenon since the effective index of refraction of water changes (Bravais' index of refraction for inclined rays applies).

Other experiments use small liquid drops, see text above. Depiction of the rainbow in the Book of Genesis Rainbows occur frequently, and have been used in the arts.

One of the earliest literary occurrences of a rainbow is in the chapter 9, as part of the flood story of Noah, where it is a sign of God's covenant to never destroy all life on earth with a global flood again. In, the rainbow bridge connects the world of men () and the realm of the gods ().

Was the god of the rainbow for the in present-day and when the regular rains on the were over, the people thanked him offering, and small. The Irish 's secret hiding place for his pot of gold is usually said to be at the end of the rainbow. This place is appropriately impossible to reach, because the rainbow is an optical effect which cannot be approached. Rainbows sometimes appear in heraldry too, even if its characteristic of multiple colours doesn't really fit into the usual heraldic style. Have been used for centuries. It was a symbol of the Cooperative movement in the in the 16th century, of peace in Italy, and of and since the 1970s.

In 1994, Archbishop and President described newly democratic post- South Africa as the. The rainbow has even been used in technology product logos including the logo. Many political alliances spanning multiple political parties have called themselves a '. Image gallery •.