Physics 1230: Light and Color Ch. 3: Mirrors and Lenses Ivan SmalyukhSlide 2Slide 3Slide 4What is a spherical convex mirror? (Think of the rear view mirror on your car)Mirrors curved like a cylinder can make you look fat or skinnyA concave mirror bulges away from youWhy are the rays from a distant light source such as the sun or a star essentially parallel?Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Here is how we use those rays to find the image of an object in a concave mirrorSpecial rays 1, 2 and 3 are not necessary to find the image of an object but are easier to work with than othersWhat happens to his image if Alex is closer to the mirror than the focal point?InformatiuonHW#2Concept questionLensesSlide 26Slide 27Slide 28Slide 29Focal point of a converging lens is where image of a distant object (sun) liesUnlike a mirror there are two focal points of a lens, one on either sideCan we be more precise with distances and magnifications?How to use rays of type 1, 2 and 3 to find the image produced by a thin converging lensWhere is the image when Alex is close to the converging lens (closer than F)?Compare the results of ray tracing to find an image of Alex for each of his two positions.What happens if we put a translucent screen at the location of the real image?Slide 37How does a diverging lens differ from a converging lens?Slide 39Slide 40Slide 41Slide 42As a pencil moves closer to a converging lens what happens to its image?Sept 24Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51The lens equation gives the same results as ray-tracing but without any rays!Here is one example of how to use the lens eqn with a converging lensHere is a sketch to show the previous resultHere is an example of how to use the lens eqn with a diverging lens (see Fig. 3.28)Summary of the meaning of negative number in the lens and magnification equationsSlide 57Slide 58Slide 59We can find the magnification of the image relative to the object by using another formulaNow find the magnification using the magnification equationThe "power," P, of a lens is equivalent to the focal length, f. One can be found from the other.Slide 63Slide 64Slide 65Slide 66Question:Slide 68Slide 69Slide 70Slide 71Slide 72Slide 73Slide 74Question for class (doesn't count)How do you feel about using the clickers (doesn't count)?Aside from whether or not you like them, do you find the clicker questionsWhich phrase best describes your opinion of the class lectures?Exam: September 29, regular class timeExam information1•Building on concepts from the last chapter–Now that we know how rays and images work we can understand how curved mirrors and lenses produce images–Practical applications include magnifying mirrors, rear-view mirrors, glasses and contact lenses, and cameras.•Spherical mirrors–Significance of focal point–Tracing reflected rays to find virtual images in convex mirrors–Tracing reflected rays to find virtual and real images in concave mirros •Lenses–Significance of focal points, focal lengths, focal planes and power of a lens–Tracing rays to find images from thin convex and concave lenses. –Fresnel lenses–Compound lenses and using intermediate images to find final imagesPhysics 1230: Light and ColorCh. 3: Mirrors and Lenses Ivan SmalyukhWhat is a spherical convex mirror? (Think of the rear view mirror on your car)•A convex mirror bulges outwards towards youReflecting surface ofconvex spherical mirrorAxis of mirrorCenter of sphereMirrors curved like a cylinder can make you look fat or skinnyLooking at yourself in a convex mirror,the image is compressed vertically likerear view mirror but in one dimension only.Your image looks fatLooking at yourself in a concave mirror, the image isvertically expanded like a bathroom magnifying mirrorbut in one dimension only. Your image looks skinnyVirtual imageon other side of mirror iscompressedverticallyVirtual imageon other side of mirror isstretchedverticallyA concave mirror bulges away from you•The center of the sphere (circle) is in front of the mirror•The focal length is also in front of the mirror, halfway between the center and the mirror surfaceAxisCenterFocalpointMirrorsurfaceWhy are the rays from a distant light source such as the sun or a star essentially parallel?Here the rays from a distant light sourcesuch as the sunBy the time they arrive here(into a camera or mirror) onlythe nearby almost parallel rays enterConvex mirrorConvex mirrorRays which arrive at the mirrorfrom a close source, like Alex’snose are not almost parallelWhenever we speak of incoming parallel rays you can always visualize rays from the sun or a star.http://micro.magnet.fsu.edu/primer/java/mirrors/concavemirrors/index.htmlhttp://micro.magnet.fsu.edu/primer/java/mirrors/convexmirrors/index.html http://micro.magnet.fsu.edu/primer/java/mirrors/convexmirrors3d/index.htmlhttp://micro.magnet.fsu.edu/primer/java/mirrors/concave.htmlhttp://micro.magnet.fsu.edu/primer/java/mirrors/convex.htmlHere is how we use those rays to find the image of an object in a concave mirror•Where is Alex's image when he is between the center and it's focal point?•Let's find the image of his nose–Here is a ray of type 1 from his nose reflecting off the mirror–Here is a ray of type 3 from his nose reflecting off the mirror–The image of the nose is at the intersection of reflected rays of type 1 and type 3. Why?–Can we use a ray of type 2?•Here is Alex's image–Is it (a) real or (b) virtual? –Magnified or reduced?•From which points can your eye see his nose?•From all points (A, B, C)?•From A and C, but not B?•From B and C, but not A?•From A only?•From C onlyCenterFocalpointMirrorsurfaceAxisABCClicker QuestionSpecial rays 1, 2 and 33 are not necessary to find the image of an object but are easier to work with than othersSpecial rays 1, 2 and 33 are not necessary to find the image of an object but are easier to work with than others•Here are rays 1 and 3 used to find the image Alex's nose•Here are some other (less convenient) incident and reflected rays–They all go through the same image point as rays 1 and 3 after satisfying the law of specular reflection!–Any two rays from an object point will intersect at the image point but rays 1, 2 and 3 are the easiest to use to find the image pointWhat happens to his image if Alex is closer to the mirror than the focal point?CenterFocalpointMirrorsurface•Draw rays of type 1