Physics
Diffraction
Diffraction refers to the bending of waves around obstacles and the spreading of waves as they pass through narrow openings. In the context of physics, it is a phenomenon that occurs with all types of waves, including sound, light, and water waves. Diffraction patterns can be observed when waves encounter obstacles or pass through slits, leading to the spreading and interference of the wave fronts.
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12 Key excerpts on "Diffraction"
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Library Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 4 Diffraction The intensity pattern formed on a screen by Diffraction from a square aperture ________________________ WORLD TECHNOLOGIES ________________________ Generation of an interference pattern from two-slit Diffraction ________________________ WORLD TECHNOLOGIES ________________________ Colors seen in a spider web are partially due to Diffraction, according to some analyses Diffraction refers to various phenomena which occur when a wave encounters an obstacle. It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Similar effects are observed when light waves travel through a medium with a varying refractive index or a sound wave through one with varying acoustic impedance. Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, x-rays and radio waves. As physical objects have wave-like properties (at the atomic level), Diffraction also occurs with matter and can be studied according to the principles of quantum mechanics. While Diffraction occurs whenever propagating waves encounter such changes, its effects are generally most pronounced for waves where the wavelength is on the order of the size of the diffracting objects. If the obstructing object provides multiple, closely-spaced openings, a complex pattern of varying intensity can result. This is due to the superposition, or interference, of different parts of a wave that traveled to the observer by different paths. The formalism of Diffraction can also describe the way in which waves of finite extent propagate in free space. For example, the expanding profile of a laser beam, the beam shape of a radar antenna and the field of view of an ultrasonic transducer are all explained by Diffraction theory.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 3 Diffraction The intensity pattern formed on a screen by Diffraction from a square aperture ________________________ WORLD TECHNOLOGIES ________________________ Generation of an interference pattern from two-slit Diffraction ________________________ WORLD TECHNOLOGIES ________________________ Colors seen in a spider web are partially due to Diffraction, according to some analyses Diffraction refers to various phenomena which occur when a wave encounters an obstacle. It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Similar effects are observed when light waves travel through a medium with a varying refractive index or a sound wave through one with varying acoustic impedance. Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, x-rays and radio waves. As physical objects have wave-like properties (at the atomic level), Diffraction also occurs with matter and can be studied according to the principles of quantum mechanics. While Diffraction occurs whenever propagating waves encounter such changes, its effects are generally most pronounced for waves where the wavelength is on the order of the size of the diffracting objects. If the obstructing object provides multiple, closely-spaced openings, a complex pattern of varying intensity can result. This is due to the super-position, or interference, of different parts of a wave that traveled to the observer by different paths. The formalism of Diffraction can also describe the way in which waves of finite extent propagate in free space. For example, the expanding profile of a laser beam, the beam shape of a radar antenna and the field of view of an ultrasonic transducer are all explained by Diffraction theory.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 1 Diffraction The intensity pattern formed on a screen by Diffraction from a square aperture ________________________ WORLD TECHNOLOGIES ________________________ Generation of an interference pattern from two-slit Diffraction ________________________ WORLD TECHNOLOGIES ________________________ Colors seen in a spider web are partially due to Diffraction, according to some analyses Diffraction refers to various phenomena which occur when a wave encounters an obstacle. It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Similar effects are observed when light waves travel through a medium with a varying refractive index or a sound wave through one with varying acoustic impedance. Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, x-rays and radio waves. As physical objects have wave-like properties (at the atomic level), Diffraction also occurs with matter and can be studied according to the principles of quantum mechanics. While Diffraction occurs whenever propagating waves encounter such changes, its effects are generally most pronounced for waves where the wavelength is on the order of the size of the diffracting objects. If the obstructing object provides multiple, closely-spaced openings, a complex pattern of varying intensity can result. This is due to the superposition, or interference, of different parts of a wave that traveled to the observer by different paths. The formalism of Diffraction can also describe the way in which waves of finite extent propagate in free space. For example, the expanding profile of a laser beam, the beam shape of a radar antenna and the field of view of an ultrasonic transducer are all explained by Diffraction theory.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 1 Diffraction The intensity pattern formed on a screen by Diffraction from a square aperture ________________________ WORLD TECHNOLOGIES ________________________ Generation of an interference pattern from two-slit Diffraction ________________________ WORLD TECHNOLOGIES ________________________ Colors seen in a spider web are partially due to Diffraction, according to some analyses Diffraction refers to various phenomena which occur when a wave encounters an obstacle. It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Similar effects are observed when light waves travel through a medium with a varying refractive index or a sound wave through one with varying acoustic impedance. Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, x-rays and radio waves. As physical objects have wave-like properties (at the atomic level), Diffraction also occurs with matter and can be studied according to the principles of quantum mechanics. While Diffraction occurs whenever propagating waves encounter such changes, its effects are generally most pronounced for waves where the wavelength is on the order of the size of the diffracting objects. If the obstructing object provides multiple, closely-spaced openings, a complex pattern of varying intensity can result. This is due to the super-position, or interference, of different parts of a wave that traveled to the observer by different paths. The formalism of Diffraction can also describe the way in which waves of finite extent propagate in free space. For example, the expanding profile of a laser beam, the beam shape of a radar antenna and the field of view of an ultrasonic transducer are all explained by Diffraction theory.
eBook - PDFPhysical Optics
Principles and Practices
- Abdul Al-Azzawi(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
Some of the light transmitted through the lens is reflected from the back surface. This could be reflected again from the front surface of an uncoated lens and produce a poor image, for example, on the photographic film in a camera. However, the reflections from the two film surfaces of a coated lens interfere destructively, and there is no reflection. 2.8 Diffraction The phenomenon of Diffraction was explained in the time of Newton by assuming that light is composed of small particles. This idea—that a source of light is a source of high-speed particles radiated in all directions—was held by Newton and other scientists for many years. After many more years, this idea was abandoned in favor of a wave theory of light. According to the wave theory of light, a beam of light is made up of many waves and propagates in space. By adopting the wave theory of light, a complete understanding of the phenomena of reflection, refraction, Diffraction, interference, and polarization was finally formulated on a mathematical basis at the beginning of the nineteenth century by Augustin Fresnel. The wave theory of light was further developed by the Dutch scientist and mathematician Christian Huygens (1629–1695). An experimental demonstration of Huygens’ principle is shown in Figure 2.11. Plane waves pass through a circular aperture, S, in a barrier. When light waves pass through such a small aperture and fall on a screen, an interference pattern of light and dark rings is observed on the screen. Examination of the rings sizes shows that light spreads in various directions beyond the aperture into regions where a shadow would be expected if light travelled in straight lines. This phenomenon is known as Diffraction. It can be regarded as a consequence of interference from many coherent wave sources. At times, the phenomena of Diffraction and interference are basically treated equally.
eBook - PDF- William Moebs, Samuel J. Ling, Jeff Sanny(Authors)
- 2016(Publication Date)
- Openstax(Publisher)
In the preceding chapter, we implicitly regarded slits as objects with positions but no size. The widths of the slits were considered negligible. When the slits have finite widths, each point along the opening can be considered a point source of light—a foundation of Huygens’s principle. Because real-world optical instruments must have finite apertures (otherwise, no light can enter), Diffraction plays a major role in the way we interpret the output of these optical instruments. For example, Diffraction places limits on our ability to Chapter 4 | Diffraction 145 resolve images or objects. This is a problem that we will study later in this chapter. 4.1 | Single-Slit Diffraction Learning Objectives By the end of this section, you will be able to: • Explain the phenomenon of Diffraction and the conditions under which it is observed • Describe Diffraction through a single slit After passing through a narrow aperture (opening), a wave propagating in a specific direction tends to spread out. For example, sound waves that enter a room through an open door can be heard even if the listener is in a part of the room where the geometry of ray propagation dictates that there should only be silence. Similarly, ocean waves passing through an opening in a breakwater can spread throughout the bay inside. (Figure 4.2). The spreading and bending of sound and ocean waves are two examples of Diffraction, which is the bending of a wave around the edges of an opening or an obstacle—a phenomenon exhibited by all types of waves. Figure 4.2 Because of the Diffraction of waves, ocean waves entering through an opening in a breakwater can spread throughout the bay. (credit: modification of map data from Google Earth) The Diffraction of sound waves is apparent to us because wavelengths in the audible region are approximately the same size as the objects they encounter, a condition that must be satisfied if Diffraction effects are to be observed easily.
- Swapan K Saha(Author)
- 2007(Publication Date)
- World Scientific(Publisher)
Chapter 3 Interference and Diffraction 3.1 Fundamentals of interference Principles of reflection and refraction are well explained using geometrical optics. Physical optics deals with light as a wave and the principle of linear superposition is particularly important. The most interesting cases of interference usually involve identical waves, with the same amplitude and wavelength, coming together. Consider the case of just two waves, although one may generalize to more than two. When these waves are in phase and travel together are superposed, the intensity at the point of superposition varies from point to point between maxima which exceed the sum of the intensities in the beams, and minima, which may be zero. This is known as interference. When the crest of one wave passes through the crest of another wave, it is referred as constructive interference. It also occurs when the trough of one wave is superpositioned upon the trough of another wave. The other extreme case occurs when the trough of one corresponds with the crest of the other and tend to cancel each other out, resulting in a flat or no wave while interfering. This type of interference is referred to as destructive interference. Basic principles of optical interference has wide range of applications ranging from on-line real-time wavefront control in astronomy to experi-ments in relativity. In what follows, the principle of interference and diffrac-tion and the necessary conditions in physical applications are elucidated. 3.2 Interference of two monochromatic waves Let the two monochromatic waves E 1 and E 2 be superposed at the recom-bination point P . The correlator sums the instantaneous amplitudes of the 81 82 Diffraction-limited imaging with large and moderate telescopes fields.
eBook - PDFBionanophotonics
An Introductory Textbook
- Shuichi Kinoshita(Author)
- 2016(Publication Date)
- Jenny Stanford Publishing(Publisher)
Chapter 4 Diffraction of Light and Diffraction Grating 4.1 Diffraction in 1D Light propagates in a straight line through space. This is one of the well-known features of light. However, this description is true only when the space is uniform and there is no obstacle to hinder its propagation. If there is an obstacle, light will go round it and will diffusely propagate with extending propagation direction. This phenomenon is known as Diffraction , which is one of the typical wave natures of light. The Diffraction of light is familiar even in our daily life: When the sunlight goes though a narrow crack of a wall, one will notice that the size of a light spot casting on a floor is not the same as that of the crack, but is much larger than it. If one holds two pencils in contact up to the light, a few dark lines will be noticed between them. These phenomena are typical indications of the Diffraction of light. In the field of nanophotonics where microstructures have a size comparable with the wavelength of light or less, the Diffraction of light often plays a key role. The typical and the most familiar example is the coloring of optical disk, on which narrow tracks carrying an Bionanophotonics: An Introductory Textbook Shuichi Kinoshita Copyright c 2013 Pan Stanford Publishing Pte. Ltd. ISBN 978-981-4364-71-3 (Hardcover), 978-981-4364-72-0 (eBook) www.panstanford.com 218 Diffraction of Light and Diffraction Grating Figure 4.1 Diffraction phenomena explained by Huygens’ principle in case where a slit width is (a) narrow and (b) wide. (c) The Diffraction experiment using a slit with varying width. The slit is illuminated by a He-Ne laser with its width being narrower from top to bottom. enormous amount of data are equipped with a constant interval. The Diffraction makes the illuminating light to be diffusely reflected at each track and to be interfered with each other, which makes the optical disk rainbow-colored.
- David Halliday, Jearl Walker, Patrick Keleher, Paul Lasky, John Long, Judith Dawes, Julius Orwa, Ajay Mahato, Peter Huf, Warren Stannard, Amanda Edgar, Liam Lyons, Dipesh Bhattarai(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
Before we can discuss some of these applications, we first must discuss why Diffraction is due to the wave nature of light. Diffraction and the wave theory of light FIGURE 36.1 This Diffraction pattern appeared on a viewing screen when light that had passed through a narrow vertical slit reached the screen. Diffraction caused the light to fare out perpendicular to the long sides of the slit. That faring produced an interference pattern consisting of a broad central maximum plus less intense and narrower secondary (or side) maxima, with minima between them. Ken Kay/Fundamental Photographs In chapter 35 we defined Diffraction rather loosely as the flaring of light as it emerges from a narrow slit. More than just flaring occurs, however, because the light produces an interference pattern called a Diffraction pattern. For example, when monochromatic light from a distant source (or a laser) passes through a narrow slit and is then intercepted by a viewing screen, the light produces on the screen a Diffraction pattern like the one in figure 36.1. The pattern consists of a broad and intense (very bright) central maximum plus a number of narrower and less intense maxima (called secondary or side maxima) to both sides. In between the maxima are minima. Light flares into those dark regions, but the light waves cancel out one another. Such a pattern would be totally unexpected in geometrical optics: if light travelled in straight lines as rays, then the slit would allow some of those rays through to form a sharp rendition of the slit on the viewing screen instead of a pattern of bright and dark bands as we see in the photograph. As in chapter 35, we must conclude that geometrical optics is only an approximation. Edges FIGURE 36.2 The Diffraction pattern produced by a razor blade in monochromatic light. Note the lines of alternating maximum and minimum intensity.
eBook - PDF- John Matolyak, Ajawad Haija(Authors)
- 2013(Publication Date)
- CRC Press(Publisher)
The conditions for constructive or destructive interference, Equations 21.12 and 21.14, depend on both film thickness d and wavelength λ air . The film will enhance a given color ( λ air ) in those regions of the film where d satisfies Equation 21.12. We have all observed these dif-ferent colors in various regions of a nonuniform film. 394 Essential Physics © 2010 Taylor & Francis Group, LLC 21.4 SINGLE-SLIT Diffraction Diffraction is the bending of light waves as they pass by obstacles whose size is comparable to their wavelength. The obstacles may be opaque (nontransmitting) or transparent (transmitting) to the waves. Diffraction of sound waves is more easily observed than Diffraction of light waves. As an example of sound Diffraction, if you are in a room connected to a second room by an open doorway and a person, who you cannot see, is in the second room talking, you can hear them. The sound waves they create, say at 500 Hz, have a wavelength of approximately 0.68 m = 68 cm = 27 inches (v sound = 340 m/s). The width of a typical interior doorway is 32 inches. The “obstacles,” that is, “slit” created by the doorway and the sound wavelength, are of comparable size, so the “bending” is easily observable. For Diffraction of light, consider a single narrow slit of width a, cut in an opaque plane, and viewed as in Figure 21.7. The source of the light S is placed at the focal point F of a converging lens. After refraction, the rays are paraxial. The wavefronts are perpendicular to the rays and all points on a given wavefront are in phase. Note that the time of travel from source through the lens, for the three rays shown, is equal; that is, the three optical paths are equal. Thus, the lens does not cause a phase difference between the rays. The wavefronts pass through the slit and illuminate a screen located a distance L from the slit plane.
eBook - PDF- Daniel Malacara(Author)
- 2001(Publication Date)
- CRC Press(Publisher)
2 Basic Wave Optics GLENN D. BOREMAN University of Central Florida, Orlando, Florida 2.1 Diffraction If one looks closely at the edges of shadows-the transition regions between bright and darkness-the transition is not abrupt as predicted by geometrical optics. There are variations in irradiance-interference fringes-seen at the boundary. As the size of the aperture is reduced, we expect that the size of the illuminated region in the observation plane will decrease also. This is true, but only to a certain point, where decreasing the dimensions of the aperture will produce spreading of the observed irradiance distribution. Huygens' principle can be used to visualize this situation qualitatively. Each point on the wavefront transmitted by the aperture can be considered a source of secondary spherical waves. The diffracted wave is the summation of the secondary sources, and the envelope of these spherical waves is the new diffracted wavefront. For an aperture whose width is large compared with the wavelength of the radiation, the transmitted wavefront has very nearly the direction of the original wavefront, and the spreading caused by truncation of the spherical waves at the edges of the aperture is negligible. However, when the aperture is sufficiently small that it con- tains only a few Huygens' sources, the transmitted wavefront will exhibit a large divergence angle. A single Huygens' source would emit uniformly in all directions as a spherical wave. We can put this phenomenon on a quantitative basis as follows. Let a scalar field V represent an optical disturbance (like the magnitude of the electric field, but a scalar rather than a vector), where V 2 is proportional to irradiance. This field V satisfies the scalar wave equation 39
eBook - PDF- L.H. Schwartz(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
tThe wavefront emitted from a single scattering point is spherical, but may be considered as a plane wave when viewed by a small sample far from the source. When this plane wave approximation is sound, the resultant Diffraction is known as Fraunhofer Diffraction. On the other hand, when the spherical wavefront must be considered, the resultant is known as Fresnel Diffraction. 80 3.1. Diffraction FROM A GRATING 81 A λ ^ / / A 0 — vt—*- / Ν / / ' Ν / / N / / FIG. 3 -1. A cosine wave moving to the right. FIG. 3-2. Interference between two waves. Both waves are assumed to have the same maximum amplitude (unity) except in (c) and the same wavelength in all cases, (a) Con-structive interference; (b) complete destructive interference; (c) partial destructive interfer-ence. One of the earliest demonstrations of the fact that electromagnetic radia-tion (visible light) can produce interference effects was performed in 1800 by the English scientist Thomas Young. In his so-called two-slit experiment, Young allowed light to pass through an opaque screen containing two tiny slits. The transmitted light from the two slits produced an interference pat-tern of low and high intensity which could be understood by arguments such as led to Fig. 3-2. Young's two-slit experiment is discussed in every 82 3. THE NATURE OF Diffraction elementary physics text as it was crucial in establishing the wave nature of light. We shall consider here a generalization of Young's experiment, using a very large number of parallel slits, all the same width, and spaced at regular intervals d as shown in Fig. 3-3. Such an arrangement of slits is known as a Diffraction grating. Radiation incident on the grating from the left is transmitt-ed through all the slits, and these transmitted beams interfere, producing a pattern called a Diffraction pattern. When this Diffraction pattern is observed at a distance R very large compared to d, the contribution of each beam may be taken as a plane wave.
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