bend
|
the art of refraction
Front cover: The curvature of a glass sphere causes images to flip over, a result of refracted light. This digital collage imitates the effect of bent light, juxtaposed with geometric angles.
Copyright Š 2014 Christina Shook Text copyright Š 1998 Paul G. Hewitt, from Conceptual Physics, 8th ed. Published by Addison Wesley. All Rights Reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any other information storage and retrieval system, without prior permission in writing from the publisher. Printed and bound in Oakland, California.
bend
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the art of refraction
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“In the right light, at the right time, everything is extraordinary.” — aaron rose
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Thread is composed of multiple strands of cotton wound together, similar to how a ray of white light contains many frequencies of radiant energy. By encasing thread in letterforms made of ice, refractive image distortion is produced.
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Bending light
Most of the things we see around us do not emit their own light. They are visible because they re-emit light reaching their surface from a primary source, such as the sun or a lamp, or from a secondary source, such as the illuminated sky. When light falls on the surface of a material it is either re-emitted without change in frequency or is absorbed in the material and turned into heat. When the re-emitted light bends from its original course and proceeds in straight lines from molecule to molecule within a transparent material, it is refracted, and the process is called refraction.
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The beautiful colors of rainbows are dispersed from the sunlight by millions of tiny spherical water droplets that act like prisms. We can better understand this by considering an individual raindrop. Picture a ray of sunlight as it enters a drop near its top surface. Some of the light is reflected, and the remainder is refracted into the water. At this first refraction, the light is dispersed into its spectrum of colors, violet being deviated the most and red the least.
A tiny drop of water can be an agent of refraction. The medium of cut paper was used to simulate the offset distortion created by the curvature of a drop.
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To understand how refraction works, we must study light at the molecular level.
Light waves can bend when their paths are altered, creating surreal visual effects. This photograph captures light and shadow as it bends across an angled surface.
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Particle waves
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Photons travel in a constant, wave-like motion, radiating energy as they move. This digital collage simulates the bustling, weaving movement of photons within a single ray of light.
Each element has its own chara Electrons dropping from highe an excited atom emit with each electromagnetic radiation call of which is related to the energ We think of this photon as a lo energy—a “particle” of light—w atom. The frequency of the pho to its energy.
A photon in a beam of red ligh amount of energy that correcs Another photon of twice the fr energy and is found in the ultra
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ht, for example, carries an sponds to its frequency. requency has twice as much aviolet part of the spectrum.
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acteristic set of energy levels. er to lower energy levels in h jump a throbbing pulse of led a photon, the frequency gy transition of the jump. ocalised corpuscle of pure which is ejected from the oton is directly proportional
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If many atoms in a material are excited, many photons with many frequencies are emitted that correspond to the many different levels excited. These frequencies correspond to characteristic colors of light from each chemical element. Excitation is illustrated in the aurora borealis. High-speed electrons that originate in the solar wind strike atoms and molecules in the upper atmosphere. They emit light exactly as it occurs in a neon tube. The different colors in the aurora correspond to the excitation of different gases—oxygen atoms produce a greenish-white color, nitrogen molecules produce red-violet, and nitrogen ions produce a blue-violet color. Auroral emissions are not restricted to visible light, and also include infrared, ultraviolet, and X-ray radiation.
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The ends of the visible light spectrum inspired the color scheme used throughout this book. This conceptual pattern exaggerates the movement of electromagnetic waves.
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Electromagnetic waves
All light originates from the accelerated motion of electric charges. Vibrating electric and magnetic fields regenerate each other to make up an electromagnetic wave. The fields of an electromagnetic wave are perpendicular to each other and to the direction of motion of the wave. Light is simply electromagnetic radiation within a particular frequency range. Such waves activate the “electrical antennae� in the retina of the eye. In the visible spectrum, lower frequencies of light appear red, and higher frequencies appear violet.
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The electromagnetic spectrum The electromagnetic spectrum is a continuous range of waves extending from radio waves to gamma rays. The descriptive names of the sections are merely a historical classification, for all waves are the same in nature, differing principally in frequency and wavelength; all have the same speed.
infrared
frequency: 300 ghz – 400 thz wavelength: 1 mm – 750 nm r e m ot e s, n i g h t v i s i o n
u lt r av i o l e t
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frequency: 750 thz – 30 phz wavelength: 400 nm – 10 nm s u n l i g h t, ta n n i n g
g a m m a r ay s
frequency: 15 ehz & higher wavelength: 20 pm & smaller p. e .t. i m a g i n g , c o s m i c r ay s
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radio
f r e q u e n c y : 3 h z & b e lo w wavelength: 100 km & larger a m / f m r a d i o, t e l e v i s i o n, r a d a r
microwaves
frequency: 300 mhz – 300 ghz wavelength: 1 m – 1 mm w i-f i, m i c r o w a v e o v e n s
visible
frequency: 400 thz – 770 thz wavelength: 750 nm – 390 nm v i s i o n, p h oto g r a p h y
x - r ay
frequency: 30 phz – 30 ehz wavelength: 10 nm – 10 pm m e d i c a l x-r ay, b a g g a g e s c r e e n i n g
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Refraction occurs in everyday objects and situations.
Objects in our environment can imitate the effects of refraction. Here, the natural form of a staircase is used as an agent of refraction.
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The curvature of a transparent lens determines whether it will disperse or focus light. This stylised pattern illustrates the opposite effects of converging and diverging lenses.
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Lenses
A very practical use of refraction occurs in lenses. A lens may be thought of as a set of prisms. The prisms refract incoming parallel light rays so that they converge to (or diverge from) a point. A convex lens, thicker in the middle, converges the light, and we call such a lens a converging lens. When a lens’s middle is thinner than the edges, and it diverges the light; such a lens is called a diverging lens. The prisms diverge the incident rays in a way that makes them appear to come from a single point in front of the lens. In both lenses the greatest deviation of rays occurs at the outermost prisms, for they have the greatest angle between the two refracting surfaces. No deviation occurs exactly in the middle, for in that region the glass faces are parallel to each other. Real lenses are not made of prisms, of course; they are made of a solid pieces of glass with surfaces ground usually to a circular curve.
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The moving patterns of bright and dark areas at the bottom of a pool result from the uneven surface of the water, which behaves like a blanket of undulating lenses. A fish looking upward at the sun would see the sun shining in intensity. Because of similar irregularities in the air’s atmosphere, we see the stars twinkle.
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For more information about this book and its author, please visit the companion website at: http://www.bend-book.com
This book was designed by Christina Shook, as part of the Graphic Design 1 course at the Academy of Art University, under the instruction of John Nettleton. The book was printed by the designer, using an Epson Stylus Photo 1400 inkjet printer on Epson Premium Presentation Matte paper. The book was bound by the designer in an accordion format that imitates the form of light waves. The typeface used is Alegreya Sans, designed by Juan Pablo del Peral for Huerta Tipogrรกphica in 2013.