# Reflection and Refraction. Reflection Most objects we see reflect light rather than emit their own light

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• Reflection and Refraction

• ReflectionMost objects we see reflect light rather than emit their own light.

• Principle of Least TimeFermat's principle - light travels in straight lines and will take the path of least time to strike mirror and reflect from point A to B

MIRRORWrong PathTrue Path

• Law of ReflectionThe angle of incidence equals the angle of reflection.

This is true for both flat mirrors and curved mirrors.

• MIRROR=

• Types of ReflectionSpecular Reflection - images seen on smooth surfaces (e.g. plane mirrors)

Diffuse Reflection - diffuse light coming from a rough surface (cannot see a reflection of yourself)

• Locating the Image for Plane MirrorsDraw the image the same distance behind the mirror as the object is in front.Draw a connector line from each object to each image.If the connector line passes through the mirror, the image will be seen.

• These lines are pointed to the only images that will be seen from each of the original locations (A-E) NOTE: No images will be seen from E

• Concave Mirrors

• Light from Infinite DistanceFocuses at the focal point

• Two Rules for Locating the Image for Concave MirrorsAny incident ray traveling parallel to the principal axis on the way to the mirror will pass through the focal point upon reflection

• Two Rules for Concave MirrorsAny incident ray passing through the focal point on the way to the mirror will travel parallel to the principal axis upon reflection Any incident ray traveling parallel to the principal axis on the way to the mirror will pass through the focal point upon reflection

• Virtual Image

• Real vs. Virtual ImageWhen a real image is formed, it still appears to an observer as though light is diverging from the real image locationonly in the case of a real image, light is actually passing through the image locationLight does not actually pass through the virtual image locationit only appears to an observer as though the light was emanating from the virtual image location

• Will an image ever focus at a single point with a convex mirror?Therefore, the images you see are virtual!

• RefractionRefraction is the bending of light when it passes from one transparent medium to another

This bending is caused by differences in the speed of light in the media

• WATERAIRLight BeamAIR

• WATERAIRLight BeamAIR

• Refraction ExamplesLight slows down when it goes from air into water and bends toward the normal.An Analogy: A car slows down when it goes from pavement onto gravel and turns toward the normal. An Illusion : Fish in the water appear closer and nearer the surface.

• http://cougar.slvhs.slv.k12.ca.us/~pboomer/physicslectures/secondsemester/light/refraction/refraction.html

• RefractionWATERAIRObserverTrue FishFalse Fish

• Atmospheric RefractionOur atmosphere can bend light and create distorted images called mirages.

• LensesWork due to change of direction of light due to refractionDiverging LensA lens that is thinner in the middle than at the edges, causing parallel light rays to diverge.Converging LensA lens that is thicker in the middle and refracts parallel light rays passing through to a focus.

• Diverging or Concave Lens

• CFConverging or Convex Lens

• CFConverging or Convex Lens

• CFConverging or Convex Lens

• CFConverging or Convex Lens

• CFConverging or Convex Lens

• CFConverging or Convex Lens

• CFConverging or Convex Lens

• CFConverging or Convex Lens

• CFConverging or Convex Lens

• CFConverging or Convex Lens

• Total Internal Reflection...is the total reflection of light traveling in a medium when it strikes a surface of a less dense medium

sin = n2/n1

• http://cougar.slvhs.slv.k12.ca.us/~pboomer/physicslectures/secondsemester/light/refraction/refraction.html

• WATERAIRLight SourceCritical AngleTotal Internal ReflectionRefraction49

• What Is Fiber Optics ? Transmitting communications signals over hair thin strands of glass or plasticNot a "new" technology Concept a century oldUsed commercially for last 25 years Fiber Optics Association

• Fiber Has More Capacity This single fiber can carry more communications than the giant copper cable!Fiber Optics Association

• Fiber Optic CommunicationsApplications include TelephonesInternetLANs - local area networksCATV - for video, voice and Internet connectionsUtilities - management of power gridSecurity - closed-circuit TV and intrusion sensorsMilitary - everywhere!Fiber Optics Association

• Why Use Fiber Optics?EconomicsSpeedDistanceWeight/sizeFreedom from interferenceElectrical isolationSecurity

Fiber Optics Association

• Fiber Optic ApplicationsFiber is already used in:> 90% of all long distance telephony> 50% of all local telephonyMost CATV networksMost LAN (computer network) backbonesMany video surveillance linksFiber Optics Association

• Fiber Optic ApplicationsFiber is the least expensive, most reliable method for high speed and/or long distance communicationsWhile we already transmit signals at Gigabits per second speeds, we have only started to utilize the potential bandwidth of fiber

Fiber Optics Association

• Fiber TechnologyFiber Optics Association

• Fiber TechnologyFiber Optics Association

• Fiber Optic Data LinksFiber Optics Association

• Light Used In Fiber OpticsFiber optic systems transmit using infrared light, invisible to the human eye, because it goes further in the optical fiber at those wavelengths.Fiber Optics Association

• Wavelength-Division MultiplexingFiber Optics Association

• Fiber Optic CableProtects the fibers wherever they are installedMay have 1 to over 1000 fibersFiber Optics Association

• Fiber Optic ConnectorsTerminates the fibersConnects to other fibers or transmission equipment

• Medical FiberscopesElectromagnetic radiation has played a role in medicine for decadesParticularly interesting is the ability to gain information without invasive proceduresUsing fiber optics in medicine has opened up new uses for lasers

• Fiberscope ConstructionFiberscopes were the first use of optical fibers in medicineInvented in 1957The objective lens forms a real image on the end of the bundle of fiber opticsThis image is carried to the other end of the bundle where an eyepiece is used to magnify the image

• EndoscopesAn endoscope is a fiberscope with additional channels besides those for illuminating and viewing fibersThe uses of these extra channels may includeIntroducing or withdrawing fluidsVacuum suctionScalpels for cutter or lasers for surgical applications

• Air Diamond Interfacesin = n2/n1Air nair = 1 and Diamond n2 = 2.42sin = 1.00/2.42 = 0.413sin = 0.413 = sin-1 0.413 = 24o

• http://cougar.slvhs.slv.k12.ca.us/~pboomer/physicslectures/secondsemester/light/refraction/refraction.html

• Dispersion...is the separation of white light into pure colors (ROY G. BIV). The index of refraction is higher for higher frequencies, so violet is bent the mostDispersion Examples: PrismsDiffraction GratingsCDsRaindrops

• RainbowsRaindrops refract, reflect and disperse sunlight.

Rainbows will always appear opposite of the Sun in the sky.

You cannot run from or run to a rainbow!

• The first commercial fiber optic installation was in for telephone signals in Chicago, installed in 1976. The first long distance networks were operational in the early 1980s. By 1985, most of todays basic technology was developed and being installed in the fiber optic networks that now handle virtually all long distance telecommunications.

FOTM, Chapter 2, DVVC, Chapter 10 That tiny strand of optical fiber can carry more communications signals than the large copper cable in the background and over much longer distances. The copper cable has about 1000 pairs of conductors. Each pair can only carry about 24 telephone conversations a distance of less than 3 miles.The fiber cable carries more than 32,000 conversations hundreds or even thousands of miles before it needs regeneration. Then each fiber can simultaneously carry over 150 times more by transmitting at different colors (called wavelengths) of light. The cost of transmitting a single phone conversation over fiber optics is only about 1% the cost of transmitting it over copper wire! Thats why fiber is the exclusive medium for long distance communications. These are but a few of the applications of fiber optics, as we concentrate on communications. Fiber optics are also used for lighting, signs, sensors and visual inspection (medicine and non-destructive testing).

FOTM, Chapter 2, DVVC, Chapter 10The biggest advantage of optical fiber is the fact it can transport more information longer distances in less time than any other communications medium. In addition, it is unaffected by the interference of electromagnetic radiation which makes it possible to transmit information and data with less noise and less error. Fiber is lighter than copper wires which makes it popular for aircraft and automotive applications. These advantages open up the doors for many other advantages that make the use of optical fiber the most logical choice in data transmission.FOTM, Chapter 2, DVVC, Chapter 10About the only place fiber has not become the dominant cable is desktop connections for LANs. Priced to just replace copper, it is more expensive, but