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$Math Alignment Project - Grand Erie District School First Class Web ...$

Keep in mind the following points when working with the thin lensequation (see also Table 11.8).• A concave lens has a negative focal length and a negative distanceto the image.• A convex lens has a positive focal length and either a positive ornegative distance to the image, depending where the object isplaced.• The image distance d iis positive if the image is real and negativeif the image is virtual.Table 11.8 Images Formed by Convex LensesLens Type Focal Length Distance to Object Distance to ImageConvex positive positive positive or negative dependingon object locationTake It FurtherLarge glass lenses can beextremely heavy. However,because refraction only occurs atthe surface of a lens, the middlematerial can be removed, as longas the lens surface remainscorrectly curved. These lenses arecalled Fresnel lenses, and they areused in lighthouses and overheadprojectors. Find out more abouthow Fresnel lenses areconstructed and used. Begin yourresearch at ScienceSource.Suggested Activity •D26 Inquiry Activity on page 461Example Problem 11.9A convex lens of a magnifying glass is held 2.00 cm above a page tomagnify the print. If the image produced by the lens is 3.60 cmaway and virtual, what is the focal length of the magnifying glass?GivenDistance of the object from the lens, d o= 2.00 cmDistance of the virtual image from the lens, d i= 3.60 cmRequiredFocal length of the lens, fAnalysis and Solution1 1The correct equation isf= +Substitute the values and their units, and solve the problem.1 1 1f=d+od i1f1f1= +2.00=0.222cmTake the reciprocal of both sides.f = 4.50 cm1–3.601 cmd oParaphraseThe focal length is about 4.50 cm.1d iPractice Problems1. A powerful magnifyingglass produces a real image4 mm from the convexlens. If the object wasplaced 28 mm away, whatis the focal length of thelens?2. Determine the focal lengthof a convex lens thatproduces a virtual image ata distance of 30 mm whenthe object is placed 15 mmaway.3. The objective lens of amicroscope is convex.The light from a specimen4.0 mm from the lensforms a real image10.0 mm from the lens.What is the focal length ofthis lens?Ray diagrams model the behaviour of light in mirrors and lenses.455
Example Problem 11.10Practice Problems1. A convex lens has a focallength of 15 cm.An object is placed 20 cmfrom the lens. What typeof image is formed? Howfar from the lens is theimage?2. A convex lens focussesthe light from the imageof a bacterium that is0.02 cm from the lens.If the focal length of thelens is 0.03 cm, how farfrom the lens is theimage?3. A convex lens has a focallength of 5.0 cm.If a penny is placed at thefocus, where is the imageof the penny formed?A convex lens has a focal length of 60.0 cm. A candle is placed50 cm from the lens. What type of image is formed, and how far isthe image from the lens?GivenFocal length of the convex lens, f = 60 cmDistance of the object from the lens, d o= 50 cmRequiredDistance of the image from the lens, d iAnalysis and SolutionA convex lens has a positive focal length, so f =60.0 cm1 1 1Use the thin lens formula:f=d+od i1 1 1 1Rearrange the formula ford: = –id if d oSubstitute the values and their units, and solve the problem.1 1 1d=f–id o1 1 1 1d= i 60 50cm1 –0.003333d=icmTake the reciprocal of both sides of the equation to eliminate thefractions.d i= 300 cmParaphraseSince d iis negative, the image is virtual and is located 300 cm fromthe lens.456 UNIT D Light and Geometric Optics
Page 1 and 2: 11Ray diagrams model the behaviour
Page 3: 11.1MirrorsHere is a summary of wha
Page 6 and 7: Using the Law of ReflectionThe law
Page 8 and 9: Concave MirrorsA concave mirror, al
Page 10 and 11: Solar OvensA solar oven, also calle
Page 12 and 13: Example Problem 11.3An electron mic
Page 14 and 15: Uses for Convex MirrorsIf you were
Page 16 and 17: D14 Skill Builder ActivityDrawing R
Page 18 and 19: D15 Inquiry Activity (continued)Fig
Page 20 and 21: 11.1 CHECK and REFLECTKey Concept R
Page 22 and 23: We use fibre optics systems to tran
Page 24 and 25: A ray of light is electromagnetic r
Page 26 and 27: How Light RefractsYou can picture t
Page 28 and 29: Snell’s LawThe phenomenon of refr
Page 30 and 31: At a certain angle, called the crit
Page 32 and 33: D19 Inquiry ActivityIndex of Refrac
Page 34 and 35: 11.2 CHECK and REFLECTKey Concept R
Page 36 and 37: Night vision goggles use lenses to
Page 38 and 39: Concave LensesA diverging lens is s
Page 40 and 41: Forming a Real ImageConvex lenses a
Page 44 and 45: Example Problem 11.11A camera with
Page 46 and 47: D24 Quick LabFocal LengthPurposeTo
Page 48 and 49: D26 Inquiry ActivityIdentifying the
Page 50 and 51: SCIENCEeverywhereSelf-AdjustingGlas
Page 52: 18. A student looks at the letters

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