Essential Knowledge, Skills, andProcesses• Explain the terms transparent, translucent, andopaque, and give an example of each.Plastic wrap Wax paper Aluminum FoilTransparent Translucent Opaque
Vocabulary• Transparent: materials that allow all light to passthrough• Translucent: letting light through but scattering it• Opaque: materials that do not let light through• Transmit: to send (as in sound or light). It alsomeans light passing through an object.
Essential Knowledge, Skills, andProcesses• Analyze the effects of a prism on white light anddescribe why this occurs. Explain why a rainbowoccurs.
Essential Knowledge, Skills, andProcesses• Describe the contributions of these scientists increating and using optical tools:– Galileo Galilei– Robert Hooke– Anton van Leeuwenhoek– Isaac Newton
Galileo Galilei• Italian• Lived from 1564-1642• Developed the refracting telescope• Developed the first known example of the microscope
Robert Hooke• English• Lived from 1635-1703• Devised the compound microscope and illuminationsystem• Discovered plant cells• Examined fossils with a microscope
Anton van Leeuwenhoek• Dutch; born in Holland• Lived 1632-1723• Made over 500 simple microscopes• Discovered bacteria, free-living and parasiticmicroscopic protists
Isaac Newton• English• Lived from 1643-1727• Discovered that white light was not a simple entity,but splits into a range of colors• When he passed white light through a glass prism, henoted that a spectrum of light was formed; particletheory of light• Reflecting telescope
ReflectionReflection• We describe the path of light as straight-line raysWe describe the path of light as straight-line rays• Reflection off a flat surface follows a simple rule:Reflection off a flat surface follows a simple rule:– angle in (incidence) equals angle out (reflection)– angles measured from surface “normal” (perpendicular)surface normalsameangleincident ray exit rayreflected ray
Reflection VocabularyReflection Vocabulary• Real Image –Real Image ––Image is made from “real” light raysthat converge at a real focal point sothe image is REAL–Can be projected onto a screenbecause light actually passesthrough the point where the imageappears–Always inverted
Reflection VocabularyReflection Vocabulary• Virtual Image–Virtual Image––“Not Real” because it cannot beprojected–Image only seems to be there!
Virtual Images in Plane MirrorsIf light energy doesnt flow from theimage, the image is "virtual".Rays seem to come from behindthe mirror, but, of course, theydont. It is virtually as if the rayswere coming from behind themirror."Virtually": the same as ifAs far as the eye-brain system isconcerned, the effect is the sameas would occur if the mirror wereabsent and the chess piece wereactually located at the spot labeled"virtual image".
Hall MirrorHall Mirror• Useful to think in terms ofUseful to think in terms of imagesimages“image” you“real” youmirror onlyneeds to be half ashigh as you are tall. Yourimage will be twice as far from youas the mirror.
Curved mirrorsCurved mirrors• What if the mirror isn’t flat?What if the mirror isn’t flat?– light still follows the same rules, with local surface normal• Parabolic mirrors have exact focusParabolic mirrors have exact focus– used in telescopes, backyard satellite dishes, etc.– also forms virtual image
Concave MirrorsConcave Mirrors•Curves inward•May be real or virtual image82a425d700
For a real object between f and the mirror, aFor a real object between f and the mirror, avirtual image is formed behind the mirror. Thevirtual image is formed behind the mirror. Theimage is upright and larger than the object.image is upright and larger than the object.
For a real object between C and f, a real imageis formed outside of C. The image is invertedand larger than the object.
For a real object at C, the real image isformed at C. The image is inverted and thesame size as the object.
For a real object close to the mirror but outsideof the center of curvature, the real image isformed between C and f. The image is invertedand smaller than the object.
For a real object at f, no image is formed. Thereflected rays are parallel and never converge.What size image is formed if thereal object is placed at the focalpoint f?
ConvexConvex MirrorsMirrors•Curves outward•Reduces images•Virtual images–Use: Rear view mirrors, storesecurity…CAUTION! Objects are closer than theyappear!
RefractionRefraction• Light also goesLight also goes throughthrough some thingssome things– glass, water, eyeball, air• The presence of material slows light’s progressThe presence of material slows light’s progress– interactions with electrical properties of atoms• The “light slowing factor” is called theThe “light slowing factor” is called the index of refractionindex of refraction– glass has n = 1.52, meaning that light travels about 1.5 timesslower in glass than in vacuum– water has n = 1.33– air has n = 1.00028– vacuum is n = 1.00000 (speed of light at full capacity)
n2 = 1.5n1 = 1.0ABRefraction at a plane surfaceRefraction at a plane surface• Light bends at interface between refractive indicesLight bends at interface between refractive indices– bends more the larger the difference in refractive index
Convex LensesConvex LensesThicker in the center thanThicker in the center thanedges.edges.– Lens that converges(brings together) lightrays.– Forms real imagesand virtual imagesdepending on positionof the objectThe Magnifier
Concave LensesConcave Lenses• Lenses that areLenses that arethicker at the edgesthicker at the edgesand thinner in theand thinner in thecenter.center.– Diverges light rays– All images areerect and reduced.The De-Magnifier
How You SeeHow You See• Near Sighted – Eyeball isNear Sighted – Eyeball istoo long and image focusestoo long and image focusesin front of the retinain front of the retina• Near Sightedness –Concave lenses expandfocal length• Far Sighted – Eyeball is tooFar Sighted – Eyeball is tooshort so image is focusedshort so image is focusedbehind the retina.behind the retina.• Far Sightedness – Convexlense shortens the focallength.
Essential Knowledge, Skills, andProcesses• Eyeglasses: have lensesc. Hyperopia (farsightedness)a. Normal eyeb. Myopia (nearsightedness) Corrected with concave lensCorrected with convex lensNo correction needed
Cameras, in briefCameras, in briefIn a pinhole camera, the hole is so small that light hitting any particular pointon the film plane must have come from a particular direction outside the cameraIn a camera with a lens, the same applies: that a point on the film planemore-or-less corresponds to a direction outside the camera. Lenses havethe important advantage of collecting more light than the pinhole admitspinholeimage atfilm planeobjectimage atfilm planeobjectlens