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Applications of Optics Purpose: To research technologies based on the principles of optics. Topics 1. 2. 3. 4. 5. 6. 7. Periscope Fiber optic cable Binocular Hologram Kaleidoscope Endoscope Retro-reflector Overview: Form a group of 4-5 individuals. You will be given one topic to research. Summarize the main points of the article and then write down your points on the poster paper. Notes: Technology Periscope Fiber optic cable Research notes Binocular Hologram Kaleidoscope Endoscope Retro-reflector Retro-reflector A retro-reflector a device or surface that reflects light back to its source in the same direction from which it came. Retroreflection is usually obtained in the following way: with a set of three mutually perpendicular mirrors that form a corner (a corner reflector or corner cube) Corner retro-reflectors occur in two varieties. In the more common form, the corner is literally the truncated corner of a cube of transparent material such as conventional optical glass. In this structure, the reflection is achieved either by total internal reflection or silvering of the outer cube surfaces. The second form uses mutually perpendicular flat mirrors bracketing an air space. These two types have similar optical properties. Retroreflection (sometimes called retroflection) is used on road surfaces, road signs, vehicles, and clothing (large parts of the surface of special safety clothing, less on regular coats). The Laser Ranging Retro Reflector (LR3) was a retro-reflector left on the moon by Apollo 11 astronauts. With this device scientists have been able to shine a beam at the Moon bounce it off LR3 and determine the earth-moon distance to within a few millimetres. The Apollo 11 Lunar Laser Ranging Experiment Reflective clothing Binoculars The first binoculars were generally too long and clumsy to work very well. In 1854, Italian inventor Ignatio Porro came up with a brilliant idea. Instead of passing the light straight through the tubes from end to end, Porro realized he could make the tubes much shorter by bouncing the light around inside. Porro’s design, which is still used today in many binoculars, uses two prisms to change the direction of the light beams inside the binocular tubes. The prisms also flip the image so that, unlike in a normal telescope, the image doesn’t end up upside-down when it reaches your eyes. At the front of each binocular is a lens—either an objective or a field lens. The objective or field lens magnifies the image . Fiber optic cables Fiber-optic lines are strands of optically pure glass as thin as a human hair that carry digital information over long distances. They are also used in medical imaging and mechanical engineering inspection. The light in a fiber-optic cable travels through the core (hallway) by constantly bouncing from the cladding (mirror-lined walls), a principle called total internal reflection. Because the cladding does not absorb any light from the core, the light wave can travel great distances. However, some of the light signal degrades within the fiber, mostly due to impurities in the glass. Endoscope Endoscopes consist of two distinct layers, an inner core and an outer layer of cladding. The higher refractive index core will reflect light waves off it's boundaries when the angle of incidence exceeds the critical angle for that particular material (core). The cladding helps to maintain all of the light within the endoscope and a black sheath over the endoscope will mean light from the external environment will not enter. As the light enters at an angle greater than the critical angle it will be totally internally reflected and bounce along the walls of the tubes. In this way, light is able to be bent around corners. Kaleidoscope The kaleidoscope is a tube of mirrors containing loose coloured beads or pebbles, or other small coloured objects. The viewer looks in one end and light enters the other end, reflecting off the mirrors. Typically there are two rectangular lengthways mirrors. Setting of the mirrors at 45° creates eight duplicate images of the objects, six at 60°, and four at 90°. As the tube is rotated, the tumbling of the coloured objects presents the viewer with varying colours and patterns. Any arbitrary pattern of objects shows up as a beautiful symmetric pattern because of the reflections in the mirrors. A two-mirror model yields a pattern or patterns isolated against a solid black background, while a three-mirror (closed triangle) model yields a pattern that fills the entire field. Holograms If you want to see a hologram, you don't have to look much farther than your wallet. There are holograms on most driver's licenses, ID cards and credit cards. A reflection hologram is a special kind of hologram in which a three dimensional image is visible when seen from a particular angle. It is only at this particular angle that a normal hologram is visible as a three dimensional and multicolor hologram. In a reflection hologram, how the hologram is visible in its three dimensional and multicolored version is dependent on the angle of light and the angle of the hologram. To be more precise and correct, it is the angle of the object beam and the reference beam. How the hologram is visible in its three dimensional and multicolored version is dependent on the angle of light and the angle of the hologram. To be more precise and correct, it is the angle of the object beam and the reference beam. In a reflection hologram, the image is stored inside an emulsion. This emulsion stored image is viewable only when white light falls on it. The image is reconstructed only at the point and time of the interaction of two beams of light, namely object beam and the reference beam, traveling in opposite directions. If the light falling onto the hologram is not at the accurate angle required to make the image visible, the hologram, by itself, selects the beam of light, that is falling on the required angle for it to be seen in multi-color and three dimension form, and then reconstructs the image. The extra light passes through the hologram without being reflected. Periscope A periscope's basic purpose is to allow submarine crews to see objects above the water while the ship remains submerged. A simple periscope can be constructed out of a vertical tube with mirrors placed at a 45-degree angle at the top and bottom of the tube. These devices basically collect light from an image and direct that light from one mirror at the top of the periscope to the mirror at the bottom of the periscope. A periscope's basic purpose is to allow submarine crews to see objects above the water while the ship remains submerged. A simple periscope can be constructed out of a vertical tube with mirrors placed at a 45-degree angle at the top and bottom of the tube. These devices basically collect light from an image and direct that light from one mirror at the top of the periscope to the mirror at the bottom of the periscope. A periscope uses triangular prisms to change the direction of light twice.