Prism Light Refraction

10 Key excerpts on "Prism Light Refraction"

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  eBook - PDF

  Introduction to Physics

  • John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
  • 2015(Publication Date)
  • Wiley

    (Publisher)

  When the light leaves the prism at the right face, it is refracted away from the normal. Thus, the net effect of the prism is to change the direction of the ray, causing it to bend downward upon entering the prism, and downward again upon leaving. Because the refractive index of the glass depends on wavelength (see Table 26.2), rays corresponding to different colors are bent by different amounts by the prism and depart traveling in different directions. The greater the index of refraction for a given color, the greater the bending, and Figure 26.18b shows the refractions for the colors red and violet, which are at opposite ends of the visible spectrum. If a beam of sunlight, which contains all colors, is sent through the prism, the 660 Chapter 26 | The Refraction of Light: Lenses and Optical Instruments sunlight is separated into a spectrum of colors, as Figure 26.18c shows. The spreading of light into its color components is called dispersion. In Figure 26.18a the ray of light is refracted twice by a glass prism surrounded by air. Conceptual Example 8 explores what happens to the light when the prism is surrounded by materials other than air. The physics of rainbows. Another example of dispersion occurs in rainbows, in which refraction by water droplets gives rise to the colors. You can often see a rainbow just as a storm is leaving, if you look at the departing rain with the sun at your back. When light from the sun enters a spherical raindrop, as in Figure 26.20, light of each color is refracted or bent by an amount that depends on the refractive index of water for that wavelength.

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  Physics for Scientists and Engineers

  Foundations and Connections, Extended Version with Modern Physics

  • Debora Katz(Author)
  • 2016(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  White light Glass prism B. u i (u t ) red (u t ) violet Vacuum n i Glass n t A. Mopic/Shutterstock.com Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 1224 CHAPTER 38 Refraction and Images Formed by Refraction Unless otherwise noted, all content on this page is © Cengage Learning. A device known as a prism makes use of dispersion to create a color spectrum (Fig. 38.9B). Two angles—the angle of deviation a and the measure of dispersion d—characterize the dispersion of light emerging from a prism (Fig. 38.10). The measure of dispersion (difference between the deviations for violet and red) depends on the difference between n for violet light and n for red light: The greater this difference, the greater the measure of dispersion. Rainbows Artificial devices such as prisms are not the only causes of dispersion. Dispersion also occurs naturally, creating beautiful phenomena such as rainbows (Fig. 38.11A). For you to see a rainbow, there must be water droplets in the air and the Sun must be behind you. Sunlight is refracted and reflected by the water droplets and into your eyes. These droplets are spread out in the air, and the position of each droplet deter- mines which color enters your eyes (Fig. 38.11B). The highest droplets allow red light to enter your eyes, and the lowest ones allow violet light to do so. Drops in between allow other colors to enter your eyes. Sometimes it is possible to see a second rainbow above the first. The second rainbow’s colors are reversed so that violet is on top and red is on the bottom. The reversal occurs because the sunlight that reaches the secondary rainbow’s droplets undergoes two reflections from the back side of each droplet (Fig. 38.11C). The net result is that the violet ray emerges below the red ray. FIGURE 38.10 A. The angle between the original path of the light and the path of the light that emerges from the prism is the angle of deviation a.

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  eBook - ePub

  Light and Optics

  Principles and Practices

  • Abdul Al-Azzawi(Author)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  This experiment is designed to demonstrate the theory of light by passing light through both a single prism and through prism combinations. It also demonstrates light dispersion into a spectrum by a prism. Since the index of refraction varies with the wavelength, the angles of refraction are wavelength dependent. When white light enters a prism, the colour rainbow (a sequence of red, orange, yellow, green, blue, and violet colours) exits the prism, because the refractive deviation increases steadily with decreasing wavelength. In this experiment the student will perform the following cases:

  a. Observe a laser beam passing through a right angle prism and draw the laser beam path. b. Observe a laser beam passing through a Dove prism and draw the laser beam path. c. Observe a laser beam passing through a Porro prism and draw the laser beam path. d. Observe a laser beam passing through a prism and draw the laser beam path. e. Observe a laser beam passing through prisms in different arrangements and draw the laser beam path through the prism combinations. f. Use a laser beam to calculate the index of refraction of a prism. g. Use white light passing through a prism to observe a rainbow of colours. Measure the refractive deviation angle of the rainbow colours and calculate the index of refraction of the prism. h. Mix the spectrum colours using a glass rod and tube.

  11.9.1 TECHNIQUE AND APPARATUS

  Appendix A presents the details of the devices, components, tools, and parts.

  1. 2×2 ft. optical breadboard

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  University Physics Volume 3

  • William Moebs, Samuel J. Ling, Jeff Sanny(Authors)
  • 2016(Publication Date)
  • Openstax

    (Publisher)

  Figure 1.24 (a) Different colors emerge in different directions, and so you must look at different locations to see the various colors of a rainbow. (b) The arc of a rainbow results from the fact that a line between the observer and any point on the arc must make the correct angle with the parallel rays of sunlight for the observer to receive the refracted rays. (c) Double rainbow. (credit c: modification of work by “Nicholas”/Wikimedia Commons) Dispersion may produce beautiful rainbows, but it can cause problems in optical systems. White light used to transmit messages in a fiber is dispersed, spreading out in time and eventually overlapping with other messages. Since a laser produces a nearly pure wavelength, its light experiences little dispersion, an advantage over white light for transmission of information. In contrast, dispersion of electromagnetic waves coming to us from outer space can be used to determine the amount of matter they pass through. Chapter 1 | The Nature of Light 27 1.6 | Huygens’s Principle Learning Objectives By the end of this section, you will be able to: • Describe Huygens’s principle • Use Huygens’s principle to explain the law of reflection • Use Huygens’s principle to explain the law of refraction • Use Huygens’s principle to explain diffraction So far in this chapter, we have been discussing optical phenomena using the ray model of light. However, some phenomena require analysis and explanations based on the wave characteristics of light. This is particularly true when the wavelength is not negligible compared to the dimensions of an optical device, such as a slit in the case of diffraction. Huygens’s principle is an indispensable tool for this analysis. Figure 1.25 shows how a transverse wave looks as viewed from above and from the side. A light wave can be imagined to propagate like this, although we do not actually see it wiggling through space.

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  Let There Be Light: The Story Of Light From Atoms To Galaxies (2nd Edition)

  The Story of Light from Atoms to Galaxies

  • Alex Montwill, Ann Breslin(Authors)
  • 2013(Publication Date)
  • ICP

    (Publisher)

  39 Chapter 3 Light as a Ray: Refraction Providing more than one quickest route When light crosses the boundary between two media, it changes direction. This phenomenon is called refraction. In this chapter we study the rules and applications of refraction . The basic rule is the same as always: it is Fermat’s principle of least time. We show that the principle leads to the experimentally established Snell’s law of refraction. Lenses are the most common example of the application of the laws of refraction . In making a lens, the trick is to make the shape such that all routes from a source A to a destination B on the other side of the lens take the same time, despite the fact that light traverses different thicknesses of glass on differ-ent routes. We spend the remainder of this section dealing with the geom-etry of the paths, and derive some simple formulae for lenses. Making visible things we cannot see We describe the effect of various combinations of lenses which make up optical systems. One fascinating example is the optical system of the human eye. We discuss some common eye defects and how these may be corrected using suitable lenses. Finally, we describe optical systems which enable us to look at things which are either too small or too far away to be seen with the naked eye. 40 Let There Be Light 2nd Edition 3.1 Refraction The refractive index As we all know, from experience of city traffic, if the speeds along different routes are not the same, the shortest route is not necessarily the quickest. We have seen already that in vacuum the speed of light is fixed at c = 2.99792458 × 10 8 m/s, equivalent to travelling a distance of approximately 7.5 times around the earth in one second . Light can also travel through certain ‘trans-parent’ materials such as air, water, glass or quartz, and there the speed is less than c .

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  Physics for Scientists and Engineers with Modern Physics

  • Raymond Serway, John Jewett(Authors)
  • 2018(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  This behavior is called dispersion. Because n is a function of wavelength, Snell’s law of refraction indicates that light of different wavelengths is refracted at different angles when incident on a material. 1.52 1.50 1.48 1.46 400 500 600 700 n l (nm) Acrylic Crown glass Fused quartz 1.54 Figure 34.20 Variation of index of refraction with vacuum wave- length for three materials. C B 1 2 A D u 1 u 1 u 2 This wavelet was sent out by wave 1 from point A. This wavelet was sent out at the same time by wave 2 from point B. u 2 Figure 34.19 Huygens’s con- struction for proving Snell’s law of refraction. Copyright 2019 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 34.6 Dispersion 913 Figure 34.20 shows that the index of refraction generally decreases with increas- ing wavelength. For example, violet light refracts more than red light does when passing into a material. Now suppose a beam of white light (a combination of all visible wavelengths) is incident on a prism as illustrated in Figure 34.21. The angle of deviation d (Fig. 34.15) depends on the index of refraction n, so, in turn, the angle depends on wavelength. The rays that emerge spread out in a series of colors known as the visible spectrum. These colors, in order of decreasing wavelength, are red, orange, yellow, green, blue, and violet. Newton showed that each color has a particular angle of deviation and that the colors can be recombined to form the original white light.

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  Physics

  • John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
  • 2015(Publication Date)
  • Wiley

    (Publisher)

  When light moves from one medium into another, its direction of travel changes, and this change in direction is called refraction. The human eye is an incredible optical instrument, and, as we will see, refraction plays a major role in the way it works to produce clear vision. 26 | The Refraction of Light: Lenses and Optical Instruments 721 Design Pics/SuperStock Chapter | 26 26.1 | The Index of Refraction As Section 24.3 discusses, light travels through a vacuum at a speed of c 5 3.00 3 10 8 m/s. It can also travel through many materials, such as air, water, and glass. Atoms in the material absorb, reemit, and scatter the light, however. Therefore, light travels through the material at a speed that is less than c, the actual speed depending on the nature of the material. In general, we will see that the change in speed as a ray of light goes from one material to an- other causes the ray to deviate from its incident direction. This change in direction is called refraction. To describe the extent to which the speed of light in a material medium differs from that in a vacuum, we use a parameter called the index of refraction (or refractive index). The index of refraction is an important parameter because it appears in Snell’s law of refraction, which will be discussed in the next section. This law is the basis of all the phenomena discussed in this chapter. Definition of the Index of Refraction The index of refraction n of a material is the ratio of the speed c of light in a vacuum to the speed v of light in the material: n 5 Speed of light in a vacuum Speed of light in the material 5 c v (26.1) Table 26.1 lists the refractive indices for some common substances. The values of n are greater than unity because the speed of light in a material medium is less than it is in a vacuum. For example, the index of refraction for diamond is n 5 2.419, so the speed of light in diamond is v 5 c/n 5 (3.00 3 10 8 m/s)/2.419 5 1.24 3 10 8 m/s.

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  Physics

  • John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
  • 2018(Publication Date)
  • Wiley

    (Publisher)

  The refracted ray is bent toward the normal ( 2 <  1 ). (b) When a ray of light is directed from water into air, the refracted ray in air is bent away from the normal ( 2 >  1 ). 26.2 Snell’s Law and the Refraction of Light 735 We have seen that reflection and refraction of light waves occur simultaneously at the inter- face between two transparent materials. It is important to keep in mind that light waves are composed of electric and magnetic fields, which carry energy. The principle of conservation of energy (see Chapter 6) indicates that the energy reflected plus the energy refracted must add up to equal the energy carried by the incident light, provided that none of the energy is absorbed by the materials. The percentage of incident energy that appears as reflected versus refracted light depends on the angle of incidence and the refractive indices of the materials on either side of the interface. For instance, when light travels from air toward water at perpendicular incidence, most of its energy is refracted and little is reflected. But when the angle of incidence is nearly 90° and the light barely grazes the water surface, most of its energy is reflected, with only a small amount refracted into the water. On a rainy night, you probably have experienced the annoying glare that results when light from an oncoming car just grazes the wet road. Under such conditions, most of the light energy reflects into your eyes. THE PHYSICS OF . . . rearview mirrors. The simultaneous reflection and refraction of light have applications in a number of devices. For instance, interior rearview mirrors in cars often have adjustment levers. One position of the lever is for day driving, while the other is for night driving and reduces glare from the headlights of the car behind. As Interactive Figure 26.2a indicates, this kind of mirror is a glass wedge with a back side that is silvered and highly reflect- ing.

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  Color Imaging

  Fundamentals and Applications

  • Erik Reinhard, Erum Arif Khan, Ahmet Oguz Akyuz, Garrett Johnson(Authors)
  • 2008(Publication Date)
  • A K Peters/CRC Press

    (Publisher)

  Such an array of diffracting obstacles is called a diffraction grating . Another way of creating a diffraction grating is by creating parallel grooves in a transparent sheet of material. If the grooves are 2.7. Interference and Diffraction 77 Figure 2.42. A diffraction grating lit by a D65 daylight simulator (left). The rainbow patterns on both the reflected (middle) and transmitted sides (right) are shown. close enough together ( D ≈ λ ), light is diffracted into different directions based on its wavelength. Polychromatic light sources consist of wavelengths distributed over the entire visible spectrum. Most common light sources, including daylight, are of this variety. Passing such light through a diffraction grating causes a rainbow pattern, as observed in Figure 2.42. As the sheet shown in this figure both transmits and reflects light, the rainbow pattern is seen on both sides. Figure 2.43. A DVD lit by a D65 daylight simulator. The small pits encoding the data are of the order of a wavelength, and therefore cause a diffraction pattern resulting in a set of rainbow colors. 78 2. Physics of Light A more common occurrence of color caused by diffraction is shown in Fig-ure 2.43, where a white light source is shone at a DVD. The pits encoding binary information in the reflecting layer are of the order of a wavelength and, therefore, cause a rainbow pattern. 2.8 Scattering Many optical phenomena may be described as scattering, although it is often more convenient to use specialized theories. For instance, we have described reflection and refraction of electro-magnetic waves at a boundary between two dielectrics with different indices of refraction in Section 2.5. Similarly diffraction and inter-ference can be seen as special cases of scattering [111]. Scattering is an interaction of light with particles such as single atoms, molecules, or clusters of molecules. Light can be absorbed by such particles and almost instantaneously be re-emitted.

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  Optics

  Principles and Applications

  • Kailash K. Sharma(Author)
  • 2006(Publication Date)
  • Academic Press

    (Publisher)

  Similarly for a direct vision prism combination, the mean deviation D = c D − f D = 0 (1.100) 3 Fraunhofer lines are the dark lines appearing in the solar spectrum. They arise due to absorption of solar radiation by atomic species (Hydrogen atoms for the F and C lines and sodium atoms for the D line) present in sun’s atmosphere. 50 Chapter 1: LIGHT WAVES if A c A f = n f D − 1 n c D − 1 (1.101) giving the angular separation between the F and C lines as F − C = n c D − 1 1 w c − 1 w f A c (1.102) 1.9 DISPERSION We have seen in Section 1.8 how a prism separates different colors of white light. Dispersion (separation of colors or more appropriately, variation of the index of refraction with wavelength) and absorption of light are closely related. It was noted in the introduction that absorption of light cannot be understood in classical terms, where matter is described by its bulk properties such as the permittivity and permeability. We also gave an equivalent description in terms of the complex index of refraction of the medium which provided a phenomenological basis for absorption of light during propagation. Though not explicitly stated, one may not be wrong to conclude from our treatment so far that the permittivity and index of refraction of a medium do not change with the frequency of the light field. This, however, is not true, and it is the frequency dependence of the velocity v = c/n of light in a medium which gives rise to the phenomenon of dispersion. Velocity of light in vacuum is independent of its frequency. A vacuum is therefore a non-dispersive medium. To explore the frequency dependence of the index of refraction of other media, we need to return to the atomistic nature of matter, where atoms and molecules are essentially dispersed in vacuum. An atom consists of a positively charged nucleus surrounded by a charged cloud of electrons.

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