PHY122_L20PostingAfterLecture

PHY122_L20PostingAfterLecture - PHY122 – Physics for the...

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Unformatted text preview: PHY122 – Physics for the Life Sciences II Lecture 20 The Eye and Optical Instruments HW 12 due Sunday, 20 Nov. at 8 pm Note: Clicker Channel 21 11/15/2011 Lecture 20 1 Lecture 20 2 Converging Lens, Ex. 2: object i n s i d e f an object is placed at s= 10 cm < f = 15 cm . Calculate and construct the image as before: – 3 construction lines: parallel to axis, through O , through focus – Calculation: – Note: for s < f : virtual upright image; 1 < m < ∞ 1 1 1 ' s f s =- object h s s ’ h ’ image O f f 11/15/2011 1 1 1 15 10 30 =- = - ' 30 cm s ⇒ = - ( image!) virtual ' s m s = - 30 3.0 10- = - = + ( image!) upright 1 1 1 ' ; ' s m s s f s + = = - (Too little time in Lecture 19 to present but posted online. Review briefly now.) Lecture 20 3 Diverging Lens, Ex. 1 A concave-concave lens has radii of curvature R 1 =12 , R 2 =24 cm and index of refraction n= 1.5 . Calculate the image of an object placed at s = 24 cm from the lens by i ) geometrical construction, ii ) calculation… – Construction: focal point: – 3 construction lines: parallel to axis, through O , through focus – Calculation: – Note: for s > : virtual upright image; 0 < m < 1 1 1 1 ' s f s =- sign convention: R> 0 if the center of curvature is on the OUTGOING side of the interface!! h ’ h object s image s ’ O f f All divergent rays! 11/15/2011 ( ) 1 2 1 1 1 1 n f R R =-- 1 1 0.5 12 24 =- - + 0.5 8 = - 16 cm f ⇒ = - ( image!) virtual ' s m s = - 9.6 24- = - 0.40 = + ( image!) upright 5 48 = - ' 9.6 cm s ⇒ = - 1 1 16 24 =-- (Too little time in Lecture 19 to present but posted online. Review briefly now.) Lecture 20 4 Summary Mirrors/Lenses Summary: R > for center-of-curvature on o u t g o i n g side; s and s’ > for r e a l image; if not, v i r t u a l image { 1 2 mirror glass lens in air 1 1 1 1 1 2 ( 1) ' ' n s s f R R R s f m s f s + = =-- = = - =- 1442443 lens/mirror type s > ( REAL object) s’ m= –s’/s =f /( f – s ) image type converging/ concave ( f > 0) 0 < f < s s’ > – ∞ < m < real, inverted 0 < s < f s’ < –s 1 < m < ∞ virtual, upright diverging/ convex ( f < 0) s > f < s’ < 0 < m < 1 virtual, upright flat ( f = ∞ ) s > s’ = –s m = 1 virtual, upright 11/15/2011 (Too little time in Lecture 19 to present but posted online. Review briefly now.) In this figure the image is produced by a lens. Where is the lens? 11/15/2011 Lecture 20 5 1 2 3 4 5 2% 9% 2% 75% 12% 1. at A 2. at B 3. at C 4. at D 5. at E correct 11/15/2011 Lecture 20 6 The lenses that are shown here, are they di di di diverging or con con con converging? 11/15/2011 Lecture 20 7 A. B. C. D. E. F. 2% 4% 4% 13% 56% 20% A. all are converging B. A and B are converging, C is diverging C. B and C are converging, A is diverging D. C is converging, A and B are diverging E. B is converging, A and C are diverging F. all are diverging A B C 1 1 1 ' s s f = + correct Lecture 20 8 The Eye The eye is a variable-focus, color-imaging, detection...
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PHY122_L20PostingAfterLecture - PHY122 – Physics for the...

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