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# Optics .

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Optics. Reflection Diffuse reflection Refraction Index of refraction Speed of light Snell’s law Geometry problems Critical angle Total internal reflection Brewster angle Fiber optics Mirages Dispersion. Prisms Rainbows Plane mirrors Spherical aberration
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Slide 1

﻿Optics Reflection Diffuse reflection Refraction Index of refraction Speed of light Snell\'s law Geometry issues Critical point Total interior reflection Brewster edge Fiber optics Mirages Dispersion Prisms Rainbows Plane mirrors Spherical distortion Concave and arched mirrors Focal length & sweep of ebb and flow Mirror/focal point condition Convex and inward focal points Human eye Chromatic variation Telescopes Huygens\' rule Diffraction

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Reflection Most things we see are on account of reflections, since most protests don\'t deliver their own obvious light. A great part of the light occurrence on a protest is ingested yet some is reflected. the wavelengths of the reflected light decide the hues we see. At the point when white light hits an apple, for example, essentially red wavelengths are reflected, while a significant part of the others are retained. A beam of light heading towards a protest is called an episode beam . In the event that it reflects off the protest, it is known as a reflected beam . An opposite line drawn anytime on a surface is known as a typical (simply like with ordinary constrain). The point between the episode beam and typical is known as the edge of frequency , i , and the edge between the reflected beam and the ordinary beam is known as the edge of reflection , r . The law of reflection expresses that the point of rate is constantly equivalent to the edge of reflection.

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Law of Reflection Normal line (opposite to surface) r i reflected beams episode beams i = r

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Diffuse Reflection Diffuse reflection is when light bobs off a non-smooth surface. Every beam of light still complies with the law of reflection, but since the surface is not smooth, the typical can point in an alternate for each beam. On the off chance that numerous light beams strike a non-smooth surface, they could be reflected in a wide range of bearings. This clarifies how we can see questions notwithstanding when it appears the light sparkling upon it ought not reflect toward our eyes. It likewise clarifies glare on wet streets: Water rounds in and smoothes out the harsh street surface so that the street turns out to be more similar to a reflect.

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Speed of Light & Refraction As you have effectively adapted, light is to a great degree quick, around 3  10 8 m/s in a vacuum. Light, be that as it may, is backed off by the nearness of matter. The degree to which this happens relies on upon what the light is going through. Light goes at around 3/4 of its vacuum speed (0.75 c ) in water and around 2/3 its vacuum speed (0.67 c ) in glass. The purpose behind this moderating is on the grounds that when light strikes a particle it must associate with its electron cloud. In the event that light goes starting with one medium then onto the next, and if the rates in these media contrast, then light is liable to refraction (an altering of course at the interface). Refraction of light waves Refraction of light beams

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At an interface between two media, both reflection and refraction can happen. The points of rate, reflection, and refraction are all deliberate regarding the typical. The points of frequency and reflection are dependably the same. In the event that light accelerates after entering another medium, the edge of refraction,  r , will be more prominent than the edge of frequency, as portrayed on the left. In the event that the light backs off in the new medium,  r will be not exactly the point of frequency, as appeared on the privilege. Reflection & Refraction Reflected Ray Reflected Ray Incident Ray Incident Ray  r Refracted Ray typical ordinary Refracted Ray  r

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Axle Analogy Imagine you\'re on a skateboard heading from the walkway toward some grass at a point. Your front hub is portrayed previously, then after the fact entering the grass. Your right contacts the grass first and moderates, yet your left wheel is as yet moving rapidly on the walkway. This causes a move in the direction of the typical. On the off chance that you skated from grass to walkway, similar way would be taken after. For this situation your right wheel would achieve the walkway first and accelerate, however your left wheel would even now be moving all the more gradually. The outcome this time would move in the opposite direction of the typical. Skating from walkway to grass resemble light setting out from air to an all the more overhead view "optically thick" medium like glass or water. The slower light goes in the new medium, the more it twists toward the typical. Light making a trip from water to velocities up and twists far from the ordinary. Likewise with a skateboard, light going along the typical will alter speed yet not course. walkway grass  r

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c v n = Index of Refraction, n The list of refraction of a substance is the proportion of the speed in light in a vacuum to the speed of light in that substance: Medium Vacuum Air (STP) Water (20 º C) Ethanol Glass Diamond n 1 1.00029 1.33 1.36 ~ 1.5 2.42 n = Index of Refraction c = Speed of light in vacuum v = Speed of light in medium Note that a vast list of refraction compares to a generally moderate light speed in that medium.

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Snell\'s Law  i n i n r  r Snell\'s law expresses that a beam of light curves in a manner that the proportion of the sine of the point of rate to the sine of the edge of refraction is consistent. Scientifically, n i sin  i = n r sin  r Here n i is the list of refraction in the first medium and n r is the record in the medium the light enters.  i and  r are the points of frequency and refraction, individually. Willebrord Snell

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 1 A • n 1 x A d B • y n 2 • B  2 Two parallel beams are appeared. Focuses An and B are specifically inverse each other. The top match is at one point in time, and the base combine after time t . The dashed lines interfacing the sets are opposite to the beams. In time t , point A voyages a separation x, while point B ventures a separation y . sin  1 = x/d, so x = d sin  1 sin  2 = y/d, so y = d sin  2 Speed of A: v 1 = x/t Speed of B: v 2 = y/t Snell\'s Law Derivation Continued…

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 1 A • n 1 x A d B • y n 2 • B  2 Snell\'s Law Derivation (cont.) v 1 x/t x sin  1 = So, v 2 y/t y sin  2 v 1/c sin  1/n 1 sin  1 n 2 =  v 2/c sin  2 1/n 2 sin  2 n 1  n 1 sin  1 = n 2 sin  2

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Refraction Problem #1 Goal: Find the rakish relocation of the beam in the wake of having gone through the crystal. Indications: Find the main point of refraction utilizing Snell\'s law. Discover edge ø . (Indicate: Use Geometry aptitudes.) 3. Locate the second edge of occurrence. Locate the second edge of refraction,  , utilizing Snell\'s Law 19.4712 º 79.4712 º Air, n 1 = 1 30 ° 10.5288 º Horiz. beam, parallel to base ø 15.9 º  Glass, n 2 = 1.5

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Refraction Problem #2 Goal: Find the separation the light beam dislodged because of the thick window and how much time it spends in the glass. A few clues are given. 20 º  1. Find  1 (only for the sake of entertainment). 2. To show approaching & active beams are parallel, find . 3. Discover d. 4. Discover the time the light spends in the glass. Additional practice: Find  if base medium is supplanted with air. 20 º H 2 0 n 1 = 1.3 20 º 0.504 m glass 10m n 2 = 1.5 5.2 · 10 - 8 s d H 2 0  26.4 º

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Refraction Problem #3 Goal: Find the leave edge in respect to the level. 19.8 °  = 36 ° air  = ? glass The triangle is isosceles. Episode beam is flat, parallel to the base.

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Reflection Problem Goal: Find occurrence edge in respect to even so that reflected beam will be vertical.  = 10 º  50 º focus of crescent reflect with flat base

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 n 2   n 1  b  b Brewster Angle The Brewster point is the edge of rate the produces reflected and refracted beams that are opposite. From Snell , n 1 sin  b = n 2 sin  . α =  b since  +  = 90 º, and  b +  = 90 º. β =  since  +  = 90 º, and  +  = 90 º. In this manner, n 1 sin  b = n 2 sin  = n 2 sin  = n 2 cos  b tan  b = n 2/n 1 Sir David Brewster

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Critical Angle The occurrence edge that causes the refracted beam to skim right along the limit of a substance is known as the basic point,  c . The basic point is the edge of frequency that delivers an edge of refraction of 90 º. On the off chance that the point of rate surpasses the basic edge, the beam is totally reflected and does not enter the new medium. A basic edge just exists when light is endeavoring to infiltrate a medium of higher optical thickness than it is at present going in. n r n i  c From Snell , n 1 sin  c = n 2 sin 90 Since transgression 90 = 1, we have n 1 sin  c = n 2 and the basic point is n r  c = sin - 1 n i

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Critical Angle Sample Problem Calculate the basic plot for the jewel air limit. Allude to the Index of Refraction graph for the data.  c = sin - 1 ( n r/n i ) = sin - (1/2.42) = 24.4  Any light shone on this limit past this edge will be reflected once again into the precious stone. air jewel  c

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Total Internal Reflection Total interior reflection happens when light endeavors to go from an all the more optically thick medium to a less optically thick medium at an edge more noteworthy than the basic point. At the point when this happens there is no refraction , just reflection. n 1 n 2 > n 1 n 2  >  c Total inward reflection can be utilized for pragmatic applications like fiber optics.

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Fiber Optics Fiber optic lines are strands of glass or straightforward filaments that permits the transmission of light and advanced data over long separations. They are utilized for the phone framework, the satellite TV framework, the web, medicinal imaging, and mechanical building examination. spool of optical fiber Optical filaments have numerous focal points

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