MirrorsPAL #19 EM WavesSlide 3Slide 4Plane MirrorSpherical MirrorsConcave and ConvexRay Drawing1) A ray that that is initially parallel to the central axis reflects through the focal pointSlide 103) A ray that reflects from the mirror at the intersection with the central axis reflects symmetrically about the central axisMirror EquationMagnificationConcaveConvexNext TimeSlide 17Slide 18Slide 19Slide 20Slide 21Slide 22MirrorsPhysics 202Professor Lee CarknerLecture 20PAL #19 EM WavesLaser from air to glass to water to glass to airairn=1airn=1glassn=1.52glassn=1.52watern=1.3312345PAL #19 EM WavesTo find each angle, n1 sin 1 = n2 sin 2sin-1 [(n1 / n2 ) sin 1]= 2 Input angle for each eqn is output angle from previous egn2 = sin-1 [(1 / 1.52 ) sin 20] = 3 = sin-1 [(1.52 / 1.33 ) sin 13] = 4 = sin-1 [(1.33 / 1.52 ) sin 15] = 5 = sin-1 [(1.52 / 1 ) sin ] =Mirrors Trace back the reflections of light from object O and it will converge to make image I I is distance i from mirror Images in the “real world” are called realPlane Mirror has curvature of infinityPlane mirror images: Are the same size as the object Are the same distance behind the mirror as the object is in front of iti = -pNote that distances “in the mirror” are negativeSpherical Mirrors The center of curvature (C) is the center of the sphere that the mirror is a section ofA distance r from the mirror The distance to the center of the mirror from the focal point is the focal length (f)f = ½ rConcave and ConvexConcave mirror: The center of curvature is in front of the mirror The image is larger than the objectConvex mirror: The center of curvature is behind mirror The image is smaller than the objectRay DrawingCan find image properties by drawing rays from object to imageFirst draw (to scale): mirror (including curvature) center of curvature (at r) Follow ray drawing rules for two rays from top of objectWhere they intersect is top of image1) A ray that that is initially parallel to the central axis reflects through the focal point2) A ray that passes through the center of curvature reflects back along itself3) A ray that reflects from the mirror at the intersection with the central axis reflects symmetrically about the central axisMirror EquationWhere are the images and how large are they? When measuring from the center of the mirror: i is the distance to the image when I and F are on the back side of the mirror i and f are negative 1/p + 1/i = 1/fMagnification If h is the height of the object and h’ is the height of the image, then the magnification is given by:|m| = h’/h m = -i/pFor m = 1, image and object are same size For |m| < 1, image is smallerIf m is negative, image is invertedConcave Produces a upright, virtual imageConcave mirrors are used to provide magnification (e.g. a shaving or make-up mirror) Produces an inverted, real imageA real image is projected onto something, it is not behind the mirrorConvexFor a convex mirror:The center of curvature is behind the mirror The image is closer to the mirror (|i| < p)The image is smaller than the objectNext TimeRead: 34.7-34.8What is the proper equation for I1?A) ½ I0B) I0 cos2 90C) I0 cos2 6D) ½ I0 cos2 E) ½ I0 cos2 6What is the proper equation for I2?A) ½ I1B) I0 cos2 C) I0 cos2 6D) ½ I0 cos2 E) ½ I0 cos2 6What is the proper equation for I3?A) ½ I2B) ½ I0 cos2 C) I0 cos2 6cos2 6D) ½ I0 cos2 60 cos2 3E) ½ I0 cos2 6cos2 6If you removed the middle polarizer, what would be the intensity I3?A) 0B) ½ I0 cos2 45C) I0 cos2 6 0 cos2 6D) ½ I0 cos2 60 cos2 3E) ½ I0 cos2 6cos2 6What is the direction of polarization of polarized sunglasses?A) Left - rightB) Up - downC) At a 45 degree angle to the verticalD) One lens is up-down and one is left rightE) They could be polarized in any directionDo polarized sunglasses work on light that is not glare (not reflected)?A) No, the goggles do nothingB) Yes, but only if the light is polarized in some other wayC) Yes, but they only reduce the light by a small amountD) Yes, they make unpolarized light half as brightE) No, but they still look
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