# Lect26

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Unformatted text preview: Physics 212 Lecture 26: Lenses Lecture Lenses Physics 212 Lecture 26, Slide 1 Music Who is the Artist? A) B) C) D) E) Ramblin’ Jack Elliott Arlo Guthrie Pete Seeger Phil Ochs U. Utah Phillips Why? Last time I had to talk about Last “circles &amp; arrows” 45th anniversary of Arlo being anniversary Arlo being arrested for litterin after Thanksgiving litterin See the movie !! Physics 212 Lecture 26, Slide 2 Your Comments “Focal length. Also, do we have homework over Focal Homework 13 is now up: Due Nov 30 break? Or ever again from this point?” break? “Can you please put the preparation excersises up soon?” Can excersises “Can you explain the terms upstream and downstream?” Exam 3 Prep has been up for weeks.. Exam See course homepage Refers to position relative to lens Light flows from upstream to downstream “What is the point of having a virtual image if you What can not see it?” can “how does the index of refraction affect the how focal length?” focal YOU CAN !! Just look in the mirror Index of refraction determines how Index much light “bends” 40 “I would like to discuss how we haven't had a would country music lecture yet..” country Does Arlo count?? Does Arlo count?? 30 20 “Bacon. How come you put up peoples comments Bacon. about not putting their comments up, but you have NEVER spoken on bacon?” NEVER 10 0 05 Confused Confident Physics 212 Lecture 26, Slide 3 Refraction Snell’s Law n1sin(θ1) = n2sin(θ2) θ1 n1 n2 θ2 That’s all of the physics – all everything else is just geometry! Physics 212 Lecture 26, Slide 4 Object Location • Light rays from sun bounce off object and go in all directions – Some hits your eyes We know object’s location by where rays come from. We will discuss eyes in lecture 28… Physics 212 Lecture 26, Slide 5 Waves from object are focused by lens Physics 212 Lecture 26, Slide 6 Two Different Types of Lenses Physics 212 Lecture 26, Slide 7 Converging Lens: Consider the case where the shape of the lens is Consider such that light rays parallel to the axis of the mirror are all “focused” to a common spot a distance f behind the lens: to f f Physics 212 Lecture 26, Slide 8 Recipe for finding image: 1) Draw ray parallel to axis refracted ray goes through focus 2) Draw ray through center refracted ray is symmetric object f image You now know the position of the same point on the image Physics 212 Lecture 26, Slide 9 S &gt; 2f image is: real inverted smaller Example 111 += S...
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