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

D24 Quick LabFocal LengthPurposeTo find a good approximation of the focal length of anyconvex lens and see the relationship between thecurvature of the lens and the focal lengthMaterials & Equipment• ruler• 279 432 mm blankpaper• several flat convexlenses of different focallengthsCAUTION: Do not shine bright light into anyone’s eyes.Incandescent light sources can become very hot. Do nottouch the bulbs or block air flow around the light bulbs.Procedure1. Copy the data table below into your notes. Giveyour table a title.Lens1.2.3.4.Focal Length(cm)• ray box with severalparallel rays of light• 216 279 mm blankpaperRadius (cm)2. Use your ruler to draw a straight line lengthwiseacross the middle of the 279 432 mm paper.This line will act as the principal axis for eachlens.3. Near one end of the paper, draw a vertical linethat intersects the first line at 90°. This line will actas the axis of symmetry for each lens.4. Place the first convex lens on the principal axisaligned with the axis of symmetry as shown inFigure 11.60.Figure 11.60 Step 45. Place the ray box off the paper so that the rays willshine parallel to the principal axis through thelens. An equal number of rays should be aboveand below the principal axis.6. Look to see where the rays converge on theprincipal axis. If they converge above or below theaxis, adjust the ray box a little to make themconverge on the principal axis.7. Place a dot at the location where the raysconverge. This is the focus. Remove the lens,then measure the distance from the vertex, whichis the intersection of the principal axis and theaxis of symmetry, to the dot. Record this as thefocal length.8. Determine the radius of the lens by placing thelens on a sheet of 216 279 mm paper andtracing one side of the lens to create an arc.Reposition the lens so that the arc is extendeduntil you have traced a full circle. Measure theradius of this circle, and record it in your table.9. Repeat steps 4 to 8 for the remaining lenses.Questions10. Explain how you determined the radius of the lensonce you drew the circle.11. What is the relationship between curvature(radius) of the lens and focal length of the lens?12. Explain how you would modify this lab to make itwork for:(a) concave lenses(b) concave mirrorsRay diagrams model the behaviour of light in mirrors and lenses.459
D25 Inquiry ActivityConvex Lens ImagesSkills Reference 2SKILLS YOU WILL USE■ Conducting inquiries safely■ Using appropriate formats tocommunicate resultsQuestionHow does the distance between an object and aconvex lens affect image formation?Materials & Equipment• cardboard stand• sheet of unlined whitepaper• adhesive tape• light bulb and socketProcedure• battery and wires• 2 convex lenses withdifferent focal lengths• modelling clay• metre stickCAUTION: Do not shine bright light into anyone’s eyes.Incandescent light sources can become very hot. Do nottouch the bulbs or block air flow around the light bulbs.1. Prepare a data table that will allow you to recordthe following values. Give your table a title.Distance (cm) from bulb to lens (d o)Distance (cm) from the lens to the screen (d i)Size of the glass part of the light bulb (h o)Size of the image on the screen (h i)Orientation of the image (inverted or upright)2. Tape the paper onto the cardboard stand. This isyour “screen.”3. Measure the height of the glass part of the bulb.Record this in your notebook as the object height.4. Determine the focal length (f) of your lens asshown in Figure 11.61:• Using the modelling clay for support, place thelens in between the stand and the bulb.• Move the screen and bulb slowly inward, thenoutward, keeping the lens in the middle. At acertain distance, an inverted image of the samesize as the actual bulb will come into focus onthe screen.• Measure the distance between the bulb andlens. This measurement is equal to 2f. Divide thevalue by 2 to determine the focal length of yourlens. Record this value for f in your notebook.5. Record values in your data table for the followingplacements of the light bulb: 2.5f, 2f, 1.5f, and0.5f. In each case, you will need to move thescreen until the image comes into focus beforerecording your data. If at any time you cannot getan image on the screen, look at the bulb throughthe lens. If you see an image through the lens,estimate h i, but do not record a value for d i.6. Repeat steps 3 to 5 with another convex lens ofdifferent focal length.Analyzing and Interpreting7. (a) Is the image formed by a convex lens alwaysinverted?(b) If not, under what conditions is it upright?8. (a) What happens to h ias the bulb is movedtoward the lens?(b) What happens to d i?9. What type of image is formed when the bulb isplaced closer than one focal length?10. How does focal length affect convex lens imageformation?Skill Practice11. Draw ray diagrams to represent the images formedat the different bulb placements for both lenses.Forming ConclusionsFigure 11.61Finding the focallength of the lens12. (a) Convex lenses are often used in computerprojectors. Explain why an image changes sizeand must be refocussed when a projector ismoved closer to or farther from the screen.Use the data you have collected in this activity.(b) Explain why different projectors might haveconvex lenses of different focal lengths.460 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 42 and 43: Keep in mind the following points w
Page 44 and 45: Example Problem 11.11A camera with
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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