OpticshittChromatic DispersionSlide 4RainbowsTotal Internal ReflectionPolarization by ReflectionImagesTwo Types of ImagesA Common MiragePlane Mirrors, Point ObjectPlane Mirrors, Extended ObjectPlane Mirrors, Mirror MazeSpherical Mirrors, Making a Spherical MirrorSpherical Mirrors, Focal Points of Spherical MirrorsImages from Spherical MirrorsLocating Images by Drawing RaysProof of the magnification equationSpherical Refracting SurfacesThin LensesImages from Thin LensesLocating Images of Extended Objects by Drawing RaysTwo Lens SystemOptical Instruments, Simple Magnifying LensSlide 25Optical Instruments, Refracting TelescopeThree Proofs, The Spherical Mirror FormulaThree Proofs, The Refracting Surface FormulaThree Proofs, The Thin Lens FormulasSlide 301Optics•Electromagnetic spectrum•polarization•Laws of reflection and refraction•TIR–Images–Mirrors and lenses–Real/virtual, inverted/straight, bigger/smaller2hittThe Sun is about 1.5 X 1011 m away. The time for light to travel this distance is about:A. 4.5 x 1018 sB. 8 sC. 8 minD. 8 hrE. 8 yr3The index of refraction n encountered by light in any medium except vacuum depends on the wavelength of the light. So if light consisting of different wavelengths enters a material, the different wavelengths will be refracted differently chromatic dispersionChromatic Dispersion33-Fig. 33-19Fig. 33-20n2blue>n2redChromatic dispersion can be good (e.g., used to analyze wavelength composition of light) or bad (e.g., chromatic aberration in lenses)4Chromatic Dispersion33-Fig. 33-21Chromatic dispersion can be good (e.g., used to analyze wavelength composition of light)or bad (e.g., chromatic aberration in lenses)prismlens5Rainbows33-Fig. 33-22Sunlight consists of all visible colors and water is dispersive, so when sunlight is refracted as it enters water droplets, is reflected off the back surface, and again is refracted as it exits the water drops, the range of angles for the exiting ray will depend on the color of the ray. Since blue is refracted more strongly than red, only droplets that are closer the the rainbow center (A) will refract/reflect blue light to the observer (O). Droplets at larger angles will still refract/reflect red light to the observer.What happens for rays that reflect twice off the back surfaces of the droplets?6For light that travels from a medium with a larger index of refraction to a medium with a smaller medium of refraction n1>n1 2>1, as 1 increases, 2 will reach 90o (the largest possible angle for refraction) before 1 does.Total Internal Reflection33-1 2 2sin sin 90cn n nq = �=Fig. 33-24n1n2Critical Angle:121sincnnq-=When 2> c no light is refracted (Snell’s Law does not have a solution!) so no light is transmitted Total Internal ReflectionTotal internal reflection can be used, for example, to guide/contain light along an optical fiber7Polarization by Reflection33-Fig. 33-27Brewster’s LawApplications1. Perfect window: since parallel polarization is not reflected, all of it is transmitted2. Polarizer: only the perpendicular component is reflected, so one can select only this component of the incident polarization( )1 21 2 290sin sinsin sin 90 cosB rB rB B Bn nn n nq qq qq q q+ = �== �- =Brewster Angle:121tanBnnq-=In which direction does light reflecting off a lake tend to be polarized?When the refracted ray is perpendicular to the reflected ray, the electric field parallel to the page (plane of incidence) in the medium does not produce a reflected ray since there is no component of that field perpendicular to the reflected ray (EM waves are transverse).8 Chapter 34 One of the most important uses of the basic laws governing light is the production of images. Images are critical to a variety of fields and industries ranging from entertainment, security, and medicine In this chapter we define and classify images, and then classify several basic ways in which they can be produced. Images34-9Image: a reproduction derived from lightReal Image: light rays actually pass through image, really exists in space (or on a screen for example) whether you are looking or notVirtual Image: no light rays actually pass through image. Only appear to be coming from image. Image only exists when rays are traced back to perceived location of sourceTwo Types of Images34-objectlensreal imageobjectmirrorvirtual image10Light travels faster through warm air warmer air has smaller index of refraction than colder air refraction of light near hot surfacesFor observer in car, light appears to be coming from the road top ahead, but is really coming from sky.A Common Mirage34-Fig. 34-111Plane mirror is a flat reflecting surface.Plane Mirrors, Point Object34-Fig. 34-2Fig. 34-3Ib Ob=Identical trianglesPlane Mirror:i p=-Since I is a virtual image i < 012Each point source of light in the extended object is mapped to a point in the imagePlane Mirrors, Extended Object34-Fig. 34-4Fig. 34-513Your eye traces incoming rays straight back, and cannot know that the rays may have actually been reflected many timesPlane Mirrors, Mirror Maze34-Fig. 34-612345678912345678914Plane mirror Concave Mirror1. Center of Curvature C: in front at infinity in front but closer2. Field of view wide smaller3. Image i=p |i|>p 4. Image heightimage height = object height image height > object height 34-Fig. 34-7Plane mirror Convex Mirror1. Center of Curvature C: in front at infinity behind mirror and closer2. Field of view wide larger3. Image i=p |i|<p 4. Image heightimage height = object height image height < object height Spherical Mirrors, Making a Spherical Mirrorconcaveplaneconvex15Spherical Mirrors, Focal Points of Spherical Mirrors34-Fig. 34-8concaveconvexSpherical Mirror:12f r=r > 0 for concave (real focal point)r < 0 for convex (virtual focal point)16Start with rays leaving a point on object, where they intersect, or appear to intersect marks the corresponding point on the image.Images from Spherical Mirrors34-Fig. 34-9Real images form on the side where the object is located (side to which light is going). Virtual images form on the opposite side.Spherical Mirror:1 1 1p i f+ =Lateral Magnification:'hmh=Lateral Magnification:imp=-17Locating Images by Drawing Rays34-Fig. 34-101. A ray parallel to central axis reflects through F2. A ray that reflects from mirror after passing through F, emerges parallel to central axis3. A ray that reflects from mirror after passing
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