Lect28 - Physics 212 Lecture 28 Optical Devices Physics 212...

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Unformatted text preview: Physics 212 Lecture 28 Optical Devices Physics 212 Lecture 28, Slide 1 Music Who is the Artist? A) B) C) D) E) BB Ray Charles Solomon Burke Henry Butler Johnny Adams Otis Redding “Rediscovered” Soul singer from 60’s Absolutely Beautiful Voice Sad note: He passed this semester (Oct) Highly Recommended DVD: “One Night History of the Blues” Theme of the week: Incredible singers note: Solomon’s final album produced final by long-time Al Green producer by Physics 212 Lecture 28, Slide 2 Your Comments “Are there any definite rules to determine Are when an image is real or virtual?” when Real: s’ > 0 Virtual: s’ < 0 “Can we talk about this whole "far point" and "near Can point" stuff? It was a bit confusing. I am excited to learn why my eyes are so incredibly awful and how my contacts and glasses actually fix them.” how We will do a brief summary LENGTHY LENGTHY DEMO / CALCULATION DEMO to finish lecture “EXPLAIN IN DETAIL AND VERY VERY EXPLAIN VERY SLOWLY HOW TO DO THESE TWO SLOWLY LENS SYSTEMS... “ “I was hoping to discuss Faraday's Lae was Lae because this is the first time i've ever because i've ever heard of this. You haven't taught it in class, so ill be pretty annoyed if its on the final. I think this is a must to review if it will be making its grand appearance.” appearance. I got a lot of these.. 05 40 30 20 10 0 Confused Confident Physics 212 Lecture 28, Slide 3 How to Get a Comment Posted: A Physics Joke I have not had my comments posted in either PHYS 211 or 212 and this is have my last physics class I need to take ( I am a biologist). Before discussing my discussing what I want to see in lecture I would like to give a farewell joke. My what ke. favorite physics joke which has gotten me through alot of tough times... alot of So you have a bunch of famous physicists visiting U of I and they decide So decide to play a little game of tag in the parking lot of ISR (it's close to Loomis). to se They establish there will be no tag backs and decide that Pascal will be They will "it" first and they begin running. Well, Pascal runs up to Einstein and tags "it" ein him first. So Einstein is looking around to see whom he will tag. While this him While is going on, Newton is in the corner of the parking lot and he pulls a piece is ulls of chalk out of his pocket and begins drawing a square around himself one of mself meter on each side. Einstein, having seen this, thinks he will be an easy meter an target so he runs up, tags Newton, and yells "You're it!". But Newton just target ewton looks at him,smiles, and says "No tags backs!... I'm a Newton over a meter him,smiles and squared and that's a Pascal". I would like additional examples of the near sighted and far sighted would hted glasses. It would be helpful to have an understanding of the "weights" glasses. ights" that each concept will have on the final exam even though many topics that opics build off of one another. Thank you. build Physics 212 Lecture 28, Slide 4 Executive Summary – Mirrors & Lenses: Executive S > 2f 2f real inverted smaller 2f > S > f real inverted bigger f >S>0 f>0 concave virtual upright bigger (converging) converging f f S′ M =− S 111 += S S′ f f<0 S >0 virtual upright smaller convex (diverging) diverging f f Physics 212 Lecture 28, Slide 5 It’s always the same: 111 += S S′ f S′ M =− S You just have to keep the signs straight: s’ is positive for a real image f is positive when it can produce a real image Lens sign conventions S: S’ : f: positive if object is “upstream” of lens positive of positive if image is “downstream” of lens positive positive if converging lens Mirrors sign conventions S: S’ : f: positive if object is “upstream” of mirror positive of positive if image is “upstream” of mirror positive positive if converging mirror (concave) Physics 212 Lecture 28, Slide 6 System of Lenses • Trace rays through lenses, beginning with most upstream lens Image from first lens Becomes object for second lens Physics 212 Lecture 28, Slide 7 System of Lenses • Virtual Objects are Possible !! Object Distance is Negative !! Image from first lens Becomes object for second lens Physics 212 Lecture 28, Slide 8 Normal Eye Physics 212 Lecture 28, Slide 9 Far-sighted Converging Lens creates virtual image at person’s near point Physics 212 Lecture 28, Slide 10 10 Near-sighted Fix with diverging lens that creates virtual image at far point. Physics 212 Lecture 28, Slide 11 11 Preflight 2 BB A B Farsighted = Converging Lens Only Converging Lens can produce a Only REAL IMAGE !! REAL 70 60 50 40 30 20 10 0 Physics 212 Lecture 28, Slide 12 12 Preflight 4 BB A B C 60 50 40 30 20 10 0 θr θi d d The image is formed an equal distance BEHIND the mirror Therefore, if you stand a distance = ½ of your near point, Therefore, of the distance to the image will be the near point distance. the Physics 212 Lecture 28, Slide 13 13 Preflight 6 BB A B C D E 1. Parallel rays are transmitted and pass Parallel through focal point (f1) through 2. Those rays also pass through focal point of Those second lens (f2) and therefore are second and transmitted parallel to the axis. transmitted 3. f2 > f1 implies that the width > w1 25 20 15 10 5 0 Physics 212 Lecture 28, Slide 14 14 The Large Synoptic Survey Telescope Physics 212 Lecture 28, Slide 15 15 How to make a big telescope mirror Melt it & spin it 52,000 lbs of borosilicate glass when filled Physics 212 Lecture 28, Slide 16 16 Multiple Lenses Exercises Two converging lenses are set up as shown. The focal length of each lens is 47 cm. The object is a light bulb located 70 cm in front of the first lens. s1=70 cm f=47 cm BB What is the nature of the image from the first lens alone? (A) REAL UPRIGHT (B) REAL INVERTED s>f M =− s′ = s’ > 0 s′ s M<0 (D) VIRTUAL INVERTED PICTURES EQUATIONS 111 =− s′ f s (C) VIRTUAL UPRIGHT fs s− f Draw Rays as above real image inverted image Physics 212 Lecture 28, Slide 17 17 Multiple Lenses Exercises Two converging lenses are set up as shown. The focal length of each lens is 47 cm. The object is a light bulb located 70 cm in front of the first lens. Lens separation = 2 m s1 = 70 cm 70 f = 47 cm s1’ = 1.43 m What is the object distance s2 for lens 2? (A) s2 = -1.43 m (B) s2 = +1.43 m (C) s2 = -0.57 m BB (D) s2 = +0.57 m (E) s2 = +2.7 m THE OBJECT FOR THE SECOND LENS IS THE IMAGE OF THE FIRST LENS s2 = -0.57 OR s2 = +0.57 Image of first lens is a REAL Image object for the second lens object Physics 212 Lecture 28, Slide 18 18 Multiple Lenses Exercises Two converging lenses are set up as shown. The focal length of each lens is 47 cm. The object is a light bulb located 70 cm in front of the first lens. Lens separation = 2 m s1=70 cm f=47 cm s1’ = 1.43 m s2 = 0.57 m BB What is the nature of the FINAL image in terms of the ORIGINAL object? (A) REAL UPRIGHT (B) REAL INVERTED fs2 s2 − f s2 > f M2 = − s2′ s2 (D) VIRTUAL INVERTED PICTURES EQUATIONS s2′ = (C) VIRTUAL UPRIGHT Draw Rays as above s2’ > 0 real image RESULTS s2’ = 2.69 m M2 < 0 M = M1M2 > 0 M = 9.6 upright image Physics 212 Lecture 28, Slide 19 19 Multiple Lenses Exercises Suppose we increase the initial object distance to 74 cm BB Lens separation = 2 m s1=74 cm f=47 cm RESULTS s1’ : 1.43 m Ø 1.29 m 1.43 How does the L, the distance to the FINAL image, change? (A) L increases (B) L decreases s2’ : 2.69 m Ø 1.38 m 2.69 (C) L remains the same Step through images, one at a time WORDS Increasing s1 will decrease s1’ (moving closer to focal point would (moving increase the image distance) Decreasing s1’ will increase s2 Increasing s2 will decrease s2’ EQUATIONS 111 =− s1′ f s1 s2 = 2m − s1′ 111 =− s2′ f s2 1 increases s1′ s2 increases 1 increases s2′ Physics 212 Lecture 28, Slide 20 20 Multiple Lenses Exercises Suppose we now decrease the initial object distance to 58 cm. Applying the lens equation, we find s1’ = 2.48m Lens separation = 2 m What is the object distance s2 for lens 2? (A) s2 = -0.48 m (B) s2 = +0.48 m (C) s2 = -2.48 m s1 = 58 cm 58 f = 47 cm s1’ = 2.48 m BB (D) s2 = +2.48 m (E) s2 = +2.58 m THE OBJECT FOR THE SECOND LENS IS THE IMAGE OF THE FIRST LENS s2 = -0.48 OR s2 = +0.48 Image of first lens is a Image VIRTUAL object for the second lens second Physics 212 Lecture 28, Slide 21 21 Multiple Lenses Exercises Suppose we now decrease the initial object distance to 58 cm. Applying the lens equation, we find s1’ = 2.48m BB Lens separation = 2 m s1=58 cm f=47 cm s1’ = 2.48 m s2 = -0.48 m What is the nature of the FINAL image in terms of the ORIGINAL object? (A) REAL UPRIGHT (B) REAL INVERTED fs2 s2 − f s2 < 0 M2 = − s2′ s2 (D) VIRTUAL INVERTED PICTURES EQUATIONS s2′ = (C) VIRTUAL UPRIGHT Draw Rays as above s2’ > 0 real image RESULTS s2’ = 0.24 m M2 > 0 M = M1M2 < 0 M = -2.1 inverted image Physics 212 Lecture 28, Slide 22 22 Course Review on Tuesday • The Topics You Want to See – – – – – – – – Electric Fields/Gauss’ Law/Potential (34%) Faraday’s Law (12%) RC/RL Circuits (14%) AC Circuits (11%) Geometric Optics (13%) Magnetic Fields & Forces (7%) Electromagnetic Waves/Polarization (8%) DC Circuits (3%) • Notes on the End Game • Final Exam: 50 questions uniformly covering topics in course • may still be able to change (combined (Dec 15)/conflict (Dec 16)) • About 40 students still have not registered their iclicker About iclicker • Do it now or accept all zeroes for lectures • Course Grade: See “Course Description” link on homepage Course Physics 212 Lecture 28, Slide 23 23 ...
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