1Physics 1201Optical Instruments (Ch 25) Could easily take an entire course! We will focus on a few: human eye corrective lenses Microscope Telescopes limits of resolution CT ScanPhysics 1202Human Eye rods & cones on retina convert light to electricimpulse fovea densely packed cones sharpest image & bestcolor discrimination Image processing mostly in brain some may be done byretinal nervesPhysics 1203Human Eye Refraction most happens at cornea(n=1.376) lens (n=1.386 - 1.406) makes fineadjustments Image rate ~ 30/sec controlled by nervous system Ciliary muscles bend lens to control focus -accomodation Near point closest distance at which eye canfocus clearly = ~ 25 cm Far point varies with personPhysics 1204Correcting Visioncommon defects caused by size of eye or shape of cornea2Physics 1205Correcting Farsighted Eye lens images object further away virtual image is at person’s near pointPhysics 1206Correcting Nearsighted Eye lens images objects atinfinity to a person’s farpoint in picture, far point is17 cm near point movesfurther out with theseglasses not good for readingPhysics 1207MicroscopeObjective is usually several lenses to produce short Fo without severe aberrationsImages nearbyobjectsM = Nl/(fe fo) N = near point of eyePhysics 1208Telescopes Images distant objects Refracting telescopes use lenses not very common anymoreM = -fo/fe3Physics 1209Telescopes Reflecting telescopes use mirrorsPhysics 12010TelescopesPhysics 12011TelescopesPhysics 12012Resolution is limited by DiffractionDiffraction Limit4Physics 12013CT Scan Computer Tomography(image of slice) CAT = Computer AssistedTomographyRegular X-rayCT scanPhysics 12014CT Scan Faster imaging with multiple beams &