3 2 15 glass bb 15 case i case ii in case i light in

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Unformatted text preview: ? The rays from the bottom half still focus The image is there, but it will be dimmer !! Physics 212 Lecture 26, Slide 19 19 air water θi θi glass θ2 1.3 θ2 1.5 glass BB 1.5 Case I Case II In Case I light in air heads toward a piece of glass with incident angle θi In Case light air In Case II, light in water heads toward a piece of glass at the same angle. In Case light water heads same In which case is the light bent most as it enters the glass? I or II or Same or or (A) (B) (C) The angle of refraction in BIGGER for the water – glass interface: n1sin(θ1) = n2sin(θ2) sin(θ2)/sin(θ1) = n1/n2 Therefore the BEND ANGLE (θ1 – θ2) is BIGGER for air – glass interface Physics 212 Lecture 26, Slide 20 20 Preflight 7 BB The rays are bent more from air to glass than from water to glass Therefore, the focal length in air is less than the focal length in water We can see this also from Lensmaker’s Formula 50 40 30 20 10 0 nlens nair Physics 212 Lecture 26, Slide 21 21 Calculation A magnifying glass is used to read the fine print on a document. The focal length of the lens is 10mm. At what distance from the lens must the document be placed in order to obtain an image magnified by a factor of 5 that is NOT inverted? • Conceptual Analysis • Lens Equation: 1/s + 1/s’ = 1/f • Magnification: M = -s’/s • Strategic Analysis • Consider nature of image (real or virtual?) to determine relation between object position and focal point • Use magnification to determine object position Physics 212 Lecture 26, Slide 22 22 A magnifying glass is used to read the fine print on a document. The focal length of the lens is 10mm. At what distance from the lens must the document be placed in order to obtain an image magnified by a factor of 5 that is NOT inverted? BB Is the image real or virtual? (A) REAL (B) VIRTUAL A virtual image will be upright A real image would be inverted h h’ f h’ h f Physics 212 Lecture 26, Slide 23 23 A magnifying glass is used to read the fine print on a docum...
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This note was uploaded on 02/09/2012 for the course PHYSICS 212 taught by Professor Mestre during the Spring '11 term at University of Illinois at Urbana–Champaign.

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