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Transcript
Geometrical Optics Chapter 24 + Other Tidbits 1 On and on and on … This is a short week. 2 Schedule follows So far, no room available for problem session. Still working on it. Today we try to complete lenses. Quiz on Friday? November 2009 SUNDAY 22 MONDAY TUESDAY 23 WEDNESDAY 25 COMPLETE THIN LENS THURSDAY 26 Interference & Diffraction FRIDAY 27 SATURDAY 28 THANKSGIVING THANKSGIVING HOLIDAY PROBLEMS SOLVING 30 29 Interference Diffraction December 2009 SUNDAY MONDAY TUESDAY 1 REVIEW SESSION If Room is Available NO ROOM AVAILAVLE 6 7 OVERVIEW OF COURSE LAST DAY OF CLASS 3 8 WEDNESDAY THURSDAY FRIDAY SATURDAY 2 3 EXAMINATION #4 4 5 INTERFERENCE & DIFFRACTION 9 11 10 12 FINAL EXAM Most important case: converging lens Object to left of F1 4 Most important case: converging lens 5 Most important case: converging lens 6 Most important case: converging lens 7 Most important case: converging lens 8 Aberrations are imperfections in the optical image formed by a spherical lens (or optical mirror). There are five main aberrations: 1. Chromatic aberration. The refractive index of glass varies with wavelength. This results in different focal lengths and image magnifications for different colours. 2. Spherical aberration. Lenses with spherical surfaces have a shorter focal length at their periphery than at their centre. 3. Coma. The various circular zones of a lens produce an image of an off-axis point that is distorted radially into a comet shape known as a coma patch. 4. Curvature of field. The focal surface is not a plane but a bowl shape. 5. Astigmatism. Because a lens appears asymmetric to an off-axis beam, the image of a point is not a point but a short line radial from, or tangential to, the optic axis of the lens. These images are formed in different planes. 6. Distortion. The image magnification is greater towards the edges of the field (pincushion distortion) or less (barrel distortion) than at its centre. 9 Remember the Spectrum? 10 Dispersion Index of refraction depends on the wavelength, or color. 1 1 1 (n 1) R1 R2 f f depends on the index of refraction. 11 Chromatic Aberration 12 Example 13 Correction : achromatic lens couple 14 15 Spherical Aberration Results from the assumption of paraxial conditions. Real lenses need a wider opening, larger apertures. 16 Spherical Aberration - Correcting 17 Barrel Distortion 18 Coma 19 Some useful stuff 20 Diaphram Intensity~Area Change D by 2 will double area Fixed f stops will therefore go by factors of 2 21 Camera The intensity of the light striking the film or CCD array is proportional to the area of the lens. This is adjusted by the photographer by means of the aperture or diaphragm control. f-number is defined by focallength f f num ber aperturediameter d Ex: A lens of focal length f=50mm and an aperture diameter of 25mm has an f number of 2, often written as “f/2” 22 f stops 23 Multiplier sqrt(2) Designation sqrt(2)^2 2.0 f/2 sqrt(2)^3 2.8 f/2.8 sqrt(2)^4 4.0 f/4 sqrt(2)^5 5.6 f/5.6 sqrt(2)^6 8.0 f/8 sqrt(2)^7 11.1 f/11 sqrt(2)^8 16.0 f/16 More on Camera 24 The Microscope 25