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Chan Medric 3A305 Physics Ace Many other important inventions involve the use of refraction. Examples are cameras, LASIK operation procedure etc. Your job is to research on 5 important technological inventions that worked on the phenomenon of refraction. In your research report, include: - pictures of the inventions - how they work, using refraction 1.Glasses Though it is an extremely simple invention, glasses are one of the most important inventions in physics due to the massive amount of problems they have solved for many of those who have problems with eyesight. They are mainly made of frames bearing lenses worn in front of the eyes, normally for vision correction, eye protection, or for protection from UV rays. Modern glasses are typically supported by pads on the bridge of the nose and by temple arms placed over the ears. Eyeglass lenses are commonly made from plastic. The materials reduce the danger of breakage and weigh less than glass lenses. Some plastics also have more advantageous optical properties than glass, such as better transmission of visible light and greater absorption of ultraviolet light. Some plastics have a greater index of refraction than most types of glass, this is useful in the making of corrective lenses shaped to correct various vision abnormalities like myopia, allowing thinner lenses for a given prescription. Not all glasses are designed solely for vision correction but are worn for protection, viewing visual information or simply just for aesthetic or fashion values. Safety glasses are a kind of eye protection against flying debris or against visible and near visible light or radiation. Sunglasses allow better vision in bright daylight, and may protect against damage from high levels of ultraviolet light. How Glasses Work For nearsightedness, glasses correct the problem of the eyeball being too long to focus upon a far away image projected onto the retina. The glasses offer a concave lens that bends light rays outward, which normalizes the eyeball. In farsightedness, the eyeball is too short to focus upon objects that are near. Glasses use a convex lens that bends the light inward before it reaches the eye's lens, thereby correcting vision. History The earliest historical reference to magnification dates back to ancient Egyptian hieroglyphs in the 6th century BC, which depict "simple glass meniscal lenses". The earliest written record of magnification dates back to the 1st century AD, when Seneca the Younger, a tutor of Emperor Nero who wrote that letters, however small and indistinct, are seen enlarged and more clearly through a globe or glass filled with water. Around 1284 in Italy, Salvino D'Armate is credited with inventing the first wearable eye glasses. The earliest pictorial evidence for the use of eyeglasses, however, is Tomaso da Modena's 1352 portrait of the cardinal Hugh de Provence reading in a scriptorium. Another early example would be a depiction of eyeglasses found north of the Alps in an altarpiece of the church of Bad Wildungen, Germany, in 1403. Many theories abound for whom should be credited for the invention of traditional eyeglasses. In 1676, Francesco Redi, a professor of medicine at the University of Pisa, wrote that he possessed a 1289 manuscript whose author complains that he would be unable to read or write were it not for the recent invention of glasses. He also produced a record of a sermon given in 1305, in which the speaker, a Dominican monk named Fra Giordano da Rivalto, remarked that glasses had been invented less than twenty years previously, and that he had met the inventor. Based on this evidence, Redi credited another Dominican monk, Fra Alessandro da Spina of Pisa, with the re-invention of glasses after their original inventor kept them a secret, a claim contained in da Spina's obituary record. While the exact date and inventor may be forever disputed, it is almost certain that spectacles were invented between 1280 and 1300 in Italy. These early spectacles had convex lenses that could correct both hyperopia (farsightedness), and the presbyopia that commonly develops as a symptom of aging. Nicholas of Cusa is believed to have discovered the benefits of concave lens in the treatment of myopia (near-sightedness). However, it was not until 1604 that Johannes Kepler published in his treatise on optics and astronomy, the first correct explanation as to why convex and concave lenses could correct presbyopia and myopia. Over time, the construction of spectacle frames also evolved. Early eyepieces were designed to be either held in place by hand or by exerting pressure on the nose. Girolamo Savonarola suggested that eyepieces could be held in place by a ribbon passed over the wearer's head, this in turn secured by the weight of a hat. The modern style of glasses, held by temples passing over the ears, was developed in 1727 by the British optician Edward Scarlett. Despite the increasing popularity of contact lenses and laser corrective eye surgery, glasses remain very common, as their technology has improved. For instance, it is now possible to purchase frames made of special memory metal alloys that return to their correct shape after being bent. Other frames have spring-loaded hinges. Either of these designs offers dramatically better ability to withstand the stresses of daily wear and the occasional accident. Modern frames are also often made from strong, light-weight materials such as titanium alloys, which were not available in earlier times. Corrective lenses are used to correct refractive errors of the eye by modifying the effective focal length of the lens in order to alleviate the effects of conditions such as myopia, hyperopia or astigmatism. Another common condition in older patients is presbyopia which is caused by the eye's crystalline lens losing elasticity, progressively reducing the ability of the lens to accommodate. Power of lens The power of a lens is generally measured in diopters. Glasses correcting for myopia will have negative diopter strengths, and glasses correcting for hypermetropia will have positive diopter strengths. Glasses correcting for astigmatism require two different strengths placed at right angles in the same lens. Prescription lenses, made to conform to the prescription of an ophthalmologist or optometrist, are used to make prescription glasses, which are then verified correct using a professional lensmeter. 2. Optic Microscope Another simple yet important invention concerning physics is the optical microscope. The optical microscope is based on the magnifying lens. The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest and simplest of the microscopes. Digital microscopes are now available which use a CCD camera to examine a sample, and the image is shown directly on a computer screen without the need for optics such as eye-pieces. Other microscopic methods which do not use visible light include scanning electron microscopy and transmission electron microscopy. A simple microscope is a microscope that uses only one lens for magnification, and is the original light microscope. Van Leeuwenhoek's microscopes consisted of a small, single converging lens mounted on a brass plate, with a screw mechanism to hold the sample or specimen to be examined.Demonstrations by British microscopist have images from such basic instruments. Though now considered primitive, the use of a single, convex lens for viewing is still found in simple magnification devices, such as the magnifying glass, and the loupe. Light microscopes are able to view specimens in color, an important advantage when compared with electron microscopes, especially for forensic analysis, where blood traces may be important, for example. Components All optical microscopes share the same basic components: The eyepiece - A cylinder containing two or more lenses to bring the image to focus for the eye. The eyepiece is inserted into the top end of the body tube. Eyepieces are interchangeable and many different eyepieces can be inserted with different degrees of magnification. Typical magnification values for eyepieces include 5x, 10x and 2x. In some high performance microscopes, the optical configuration of the objective lens and eyepiece are matched to give the best possible optical performance. This occurs most commonly with apochromatic objectives. The objective lens - a cylinder containing one or more lenses, typically made of glass, to collect light from the sample. At the lower end of the microscope tube one or more objective lenses are screwed into a circular nose piece which may be rotated to select the required objective lens. Typical magnification values of objective lenses are 4x, 5x, 10x, 20x, 40x, 50x and 100x. Some high performance objective lenses may require matched eyepieces to deliver the best optical performance. The stage - a platform below the objective which supports the specimen being viewed. In the center of the stage is a hole through which light passes to illuminate the specimen. The stage usually has arms to hold slides (rectangular glass plates with typical dimensions of 25 mm by 75 mm, on which the specimen is mounted). The illumination source - below the stage, light is provided and controlled in a variety of ways. At its simplest, daylight is directed via a mirror. Most microscopes, however, have their own controllable light source that is focused through an optical device called a condenser, with diaphragms and filters available to manage the quality and intensity of the light. The objective lens is, at its simplest, a very high powered magnifying glass i.e. a lens with a very short focal length. This is brought very close to the specimen being examined so that the light from the specimen comes to a focus about 160 mm inside the microscope tube. This creates an enlarged image of the subject. This image is inverted and can be seen by removing the eyepiece and placing a piece of tracing paper over the end of the tube. By carefully focusing a brightly lit specimen, a highly enlarged image can be seen. It is this real image that is viewed by the eyepiece lens that provides further enlargement. In most microscopes, the eyepiece is a compound lens, with one component lens near the front and one near the back of the eyepiece tube. This forms an air-separated couplet. In many designs, the virtual image comes to a focus between the two lenses of the eyepiece, the first lens bringing the real image to a focus and the second lens enabling the eye to focus on the virtual image. The whole of the optical assembly is attached to a rigid arm w hich in turn is attached to a robust U shaped foot to provide the necessary rigidity. The arm is usually able to pivot on its joint with the foot to allow the viewing angle to be adjusted. Mounted on the arm are controls for focusing, typically a large knurled wheel to adjust coarse focus, together with a smaller knurled wheel to control fine focus. Updated microscopes may have many more features, including reflected light (incident) illumination, fluorescence microscopy, phase contrast microscopy and differential interference contrast microscopy, spectroscopy, automation, and digital imaging. Magnification On a typical compound optical microscope, there are three objective lenses: a scanning lens (4×), low power lens (10×)and high power lens (ranging from 20 to 100×). Some microscopes have a fourth objective lens, called an oil immersion lens. To use this lens, a drop of immersion oil is placed on top of the cover slip, and the lens is very carefully lowered until the front objective element is immersed in the oil film. Such immersion lenses are designed so that the refractive index of the oil and of the cover slip are closely matched so that the light is transmitted from the specimen to the outer face of the objective lens with minimal refraction. An oil immersion lens usually has a magnification of 50 to 100×. The actual power or magnification of an optical microscope is the product of the powers of the ocular (eyepiece), usually about 10×, and the objective lens being used. How it works The essential principle of the microscope is that an objective lens with very short focal length (often a few mm) is used to form a highly magnified real image of the object. Here, the quantity of interest is linear magnification, and this number is generally inscribed on the objective lens casing. In practice, today, this magnification is carried out by means of two lenses: the objective lens which creates an image at infinity, and a second weak tube lens which then forms a real image in its focal plane. Usage Optical microscopy is used extensively in microelectronics, nanophysics, biotechnology, pharmaceutic research and microbiology. Optical microscopy is used for medical diagnosis, the field being termed histopathology when dealing with tissues, or in smear tests on free cells or tissue fragments. 3. Telescope A telescope is an instrument designed for the observation of remote objects by the collection of electromagnetic radiation. The first known practically functioning telescopes were invented in the Netherlands at the beginning of the 17th century. "Telescopes" can refer to a whole range of instruments operating in most regions of the electromagnetic spectrum. The largest reflecting telescopes currently have objectives larger then 10 m (33 feet). The word "telescope" was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galilei's instruments presented at a banquet at the Accademia dei Lincei. History of the telescope The earliest evidence of working telescopes were the refracting telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals: Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, and Jacob Metius of Alkmaar. Galileo greatly improved upon these designs the following year. The idea that a mirror could be used as an objective instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors, primarily reduction of spherical aberration with no chromatic aberration, led to many proposed designs and several attempts to build reflecting telescopes. In 1668, Isaac Newton built the first practical reflecting telescope, which bears his name, the Newtonian reflector. The 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays. The first purpose built radio telescope went into operation in 1937. Since then, a tremendous variety of complex astronomical instruments have been developed. Optical telescopes An optical telescope gathers and focuses light mainly from the visible part of the electromagnetic spectrum (although some work in the infrared and ultraviolet). Optical telescopes increase the apparent angular size of distant objects as well as their apparentbrightness. In order for the image to be observed, photographed, studied, and sent to a computer, telescopes work by employing one or more curved optical elements—usua lly made from glass—lenses, or mirrors to gather light and other electromagnetic radiation to bring that light or radiation to a focal point. Optical telescopes are used for astronomy and in many non-astronomical instruments, including: theodolites (including transits), spotting scopes, monoculars, binoculars, camera lenses, and spyglasses. There are three main types: The refracting telescope which uses lenses to form an image. The reflecting telescope which uses an arrangement of mirrors to form an image. The catadioptric telescope which uses mirrors combined with lenses to form an image. There are also many other types of optical telescopes which include: Infrared telescopes Submillimetre telescopes Ultraviolet telescopes Fresnel Imager 4. Optical fibre The guiding of light in media using the concept of total internal reflection was first discussed during the 19th century. The idea is often attributed to J. Tyndall who demonstrated the guiding of light in a water jet at the Royal Society in London in 1854, following a suggestion by M. Faraday. Usage Optical fiber can be used as a medium for telecommunication and networking because it is flexible and can be bundled as cables. It is especially advantageous for longdistance communications, because light propagates through the fiber with little attenuation compared to electrical cables. This allows long distances to be spanned with few repeaters. Additionally, the per-channel light signals propagating in the fiber have been modulated at rates as high as 111 gigabits per second by NTT, although 10 or 40 Gb/s is typical in deployed systems. Each fiber can carry many independent channels, each using a different wavelength of light (wavelength-division multiplexing (WDM)). The net data rate (data rate without overhead bytes) per fiber is the per-channel data rate reduced by the FEC overhead, multiplied by the number of channels (usually up to eighty in commercialdense WDM systems as of 2008). The current laboratory fiber optic data rate record, held by Bell Labs in Villarceaux, France, is multiplexing 155 channels, each carrying 100 Gb/s over a 7000 km fiber. For short distance applications, such as creating a network within an office building, fiber-optic cabling can be used to save space in cable ducts. This is because a single fiber can often carry much more data than many electrical cables, such as 4 pair Cat5 Ethernet cabling.Fiber is also immune to electrical interference; there is no cross-talk between signals in different cables and no pickup of environmental noise. Non-armored fiber cables do not conduct electricity, which makes fiber a good solution for protecting communications equipment located in high voltage environments such as power generation facilities, or metal communication structures prone to lightning strikes. They can also be used in environments where explosive fumes are present, without danger of ignition. Wiretapping is more difficult compared to electrical connections, and there are concentric dual core fibers that are said to be tap-proof. Although fibers can be made out of transparent plastic, glass, or a combination of the two, the fibers used in long-distance telecommunications applications are always glass, because of the lower optical attenuation. Both multi-mode and single-mode fibers are used in communications, with multi-mode fiber used mostly for short distances, up to 550 m (600 yards), and single-mode fiber used for longer distance links. Because of the tighter tolerances required to couple light into and between single-mode fibers (core diameter about 10 micrometers), single-mode transmitters, receivers, amplifiers and other components are generally more expensive than multi-mode components. Fiber optic sensors Fibers have many uses in remote sensing. In some applications, the sensor is itself an optical fiber. In other cases, fiber is used to connect a non-fiberoptic sensor to a measurement system. Depending on the application, fiber may be used because of its small size, or the fact that no electrical power is needed at the remote location, or because many sensors can be multiplexed along the length of a fiber by using different wavelengths of light for each sensor, or by sensing the time delay as light passes along the fiber through each sensor. Time delay can be determined using a device such as an optical time-domain reflectometer. Optical fibers can be used as sensors to measure strain, temperature, pressure and other quantities by modifying a fiber so that the quantity to be measured modulates the intensity, phase, polarization, wavelength or transit time of light in the fiber. Sensors that vary the intensity of light are the simplest, since only a simple source and detector are required. A particularly useful feature of such fiber optic sensors is that they can, if required, provide distributed sensing over distances of up to one meter. Extrinsic fiber optic sensors use an optical fiber cable, normally a multi-mode one, to transmit modulated light from either a non-fiber optical sensor, or an electronic sensor connected to an optical transmitter. A major benefit of extrinsic sensors is their ability to reach places which are otherwise inaccessible. An example is the measurement of temperature inside aircraft jet engines by using a fiber to transmit radiation into a radiation pyrometer located outside the engine. Extrinsic sensors can also be used in the same way to measure the internal temperature of electrical transformers, where the extreme electromagnetic fields present make other measurement techniques impossible. Extrinsic sensors are used to measure vibration, rotation, displacement, velocity, acceleration, torque, and twisting. 5. Fabrications of refractive blazed holograms Methods and apparatus for fabricating refractive blazed holograms having high single image diffraction efficiencies. A reflective blazed hologram made with a single wavelength light source may be modified for high blazed efficiencies at any desired wavelength. A reflective blazed hologram surface is replicated onto the surface of a material of higher refractive index, with a shorter wavelength of light utilized fore reconstruction. A further embodiment is to replicate a reflective blazed hologram onto the surface of a material that can be made to undergo an isotropic dimension increase or decrease. When the desired dimension change has taken place, the blazed surface thereof would again be replicated onto the surface of a suitable transparent material of the proper refractive index. Thus, refractive blazed holograms blazed for any wavelength can be obtained Brief Summary Of The Invention In accomplishing the above and other desired aspects of the present invention, Applicant has invented improved apparatus and methods for blazed holographic information recording. In a first embodiment, a reflective blazed hologram of one constructing blaze wavelength is replicated onto the surface of a material having a different refractive index to form a refractive blazed hologram having a different blaze wavelength. A second embodiment replicates a reflective blazed hologram onto the surface of a material that can be made to undergo an isotropic dimension change. Depending upon the material to be used, a refractive blazed hologram blazed for any wavelength can be obtained. A third embodiment of the invention illustrates the replication of a reflective hologram onto a material which is isotropically expanded or shrunk, the ratio of the second wavelength to the first wavelength being the factor of multiplication thereof. Detailed Description Of The Invention As hereinabove set forth, Yu N. Denisyuk introduced the concept of a hologram produced by exposing a thick photographic emulsion to a standing optical wavefield. The standing wavefield was created by allowing light reflected from an object to interfere with a reference beam propagating in the opposite direction. The photographic emulsion recorded the antinodal surfaces of the wavefield as silver deposits in the emulsion volume. These silver deposits served as reflection surfaces for the reconstruction of the object wavefield. It may be expected that boundary conditions equivalent to a single isolated standing wave surface can be obtained by isolating the fragments of standing wave surfaces located in the volume of space between two parallel planes spaced approximately onehalf wavelength apart. Such a hologram is in effect blazed, and like a blazed diffraction grating, reflects a maximum amount of light into a single diffraction order. Its groove shape follows sections of the standing wave surfaces。 Light transmitted through an uncoated, as opposed to one coated with aluminum, for example, blazed hologram can be made to undergo a phase change of one wavelength between adjacent blaze surfaces. When this is done, light contributions from all blazed surface segments will add in phase to produce an image, and thus is produced a refractive blaze hologram. For maximum efficiency in a reflective blazed hologram it is advantageous to have the angle of diffraction coincident with the angle of reflection from the facets on the blazed surface. However, in a refractive instance for a given wavelength, when the reflective situation is optimum, the phase change is considerably distorted, causing among other things the transmitted light energy to be divided rather symmetrically among numerous images. Images from reflective blazed holograms can be reconstructed by reflecting light either from the air side or from the substrate side of the blazed surface. Because the wavelength is longer in air than in the substrate the hologram will be blazed for different wavelengths in the two cases. For purposes of illustrating the principles of this invention in the simplest manner the equation shown above and all subsequent equations assume the image is being reconstructed by reflecting light from the air side of the blazed surface, where the refractive index is 1. In the foregoing there has been disclosed methods and apparatus for effectively utilizing holographic principles in the construction of blazed holograms for refraction and for unavailable light source wavelengths. The use of transmission blazed holograms greatly enhances their potential application as optical imaging elements over the reflective blazed holograms as set forth above in the copending application. While the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt to a particular situation without departing from the essential teachings of the invention. 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