Light Mirrors and Lenses (3379.0K) - McGraw-Hill Higher Education

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ImageWallMirrorLight rays that bounce off a person strike the mirror.Some these light rays are reflected into the person’s eye.MirrorWallThe light rays that are shown entering the person’seye seem to be coming from a person behind the mirror.Reflection by Plane Mirrors Did you glance in the mirrorbefore leaving for school this morning? If you did, you probablylooked at your reflection in a plane mirror. A plane mirror is amirror with a flat reflecting surface. In a plane mirror, yourimage looks much the same as it would in a photograph.However, you and your image are facing in opposite directions.This causes your left side and your right side to switch places onyour mirror image. Also, your image seems to be coming frombehind the mirror. How does a plane mirror form an image?Figure 11 A plane mirror formsan image by changing the directionof light rays.Describe how you and your imagein a plane mirror are different.What is a plane mirror?Figure 11 shows a person looking into a plane mirror. Lightwaves from the Sun or another source of light strike each part ofthe person. These light rays bounce off the person according tothe law of reflection, and some of them strike the mirror. Therays that strike the mirror also are reflected according to the lawof reflection. Figure 11A shows the path traveled by a few of therays that have been reflected off the person and reflected back tothe person’s eye by the mirror.The Image in a Plane Mirror Why does the image you seein a plane mirror seem to be behind the mirror? This is a resultof how your brain processes the light rays that enter your eyes.Although the light rays bounced off the mirror’s surface, yourbrain interprets them as having followed the path shown by thedashed lines in Figure 11B. In other words, your brain alwaysassumes that light rays travel in straight lines without changingdirection. This makes the reflected light rays look as if they arecoming from behind the mirror, even though no source of lightis there. The image also seems to be the same distance behindthe mirror as the person is in front of the mirror.Light Waves and PhotonsWhen an object like a marbleor a basketball bouncesoff a surface, it obeys thelaw of reflection. Becauselight also obeys the law ofreflection, people oncethought that light must be astream of particles. Today,experiments have shownthat light can behave asthough it were both a waveand a stream of energy bundlescalled photons. Readan article about photonsand write a description inyour Science Journal.SECTION 2 Reflection and Mirrors 557
Topic: Concave MirrorsVisit ips.msscience.com for Weblinks to information about theconcave mirrors used in telescopes.Activity Make a chart showingthe five largest telescope mirrorsand where they are located.Concave and Convex MirrorsSome mirrors are not flat. A concave mirror has a surfacethat is curved inward, like the bowl of a spoon. Unlike planemirrors, concave mirrors cause light rays to come together, orconverge. A convex mirror, on the other hand, has a surface thatcurves outward, like the back of a spoon. Convex mirrors causelight waves to spread out, or diverge. These two types of mirrorsform images that are different from the images that are formedby plane mirrors. Examples of a concave and a convex mirrorare shown in Figure 12.What’s the difference between a concave andconvex mirror?Figure 12 Convex and concavemirrors have curved surfaces.Concave Mirrors The way in which a concave mirror formsan image is shown in Figure 13. A straight line drawn perpendicularto the center of a concave or convex mirror is called theoptical axis. Light rays that travel parallel to the optical axis andstrike the mirror are reflected so that they pass through a singlepoint on the optical axis called the focal point. The distancealong the optical axis from the center of the mirror to the focalpoint is called the focal length.The image formed by a concave mirror depends on the positionof the object relative to its focal point. If the object is fartherfrom the mirror than the focal point, the image appears tobe upside down, or inverted. The size of the image decreases asthe object is moved farther away from the mirror. If the object iscloser to the mirror than one focal length, the image is uprightand gets smaller as the object moves closer to the mirror.A concave mirror can produce a focused beam of light if asource of light is placed at the mirror’s focal point, as shown inFigure 13. Flashlights and automobile headlights use concavemirrors to produce directed beams of light.A concave mirrorhas a surface that’scurved inward.A convex mirror hasa surface that’scurved outward.558 CHAPTER 19 Light, Mirrors, and Lenses(l)Matt Meadows, (r)Paul Silverman/Fundamental Photographs
Page 2 and 3: Start-Up ActivitiesBending LightEve
Page 4: Light Travels Through Space There i
Page 7 and 8: Figure 7 The three primarycolor pig
Page 9: Figure 9 A highly magnifiedview of
Page 13 and 14: Figure 14 A convex mirror is a mirr
Page 15 and 16: Refraction and Lenses■ Determine
Page 17 and 18: Figure 18 A convexlens forms an ima
Page 19 and 20: CladdingPlastic fiberLight rayFigur
Page 21 and 22: Forming an Imagewith a LensProcedur
Page 23 and 24: ObjectDiaphragmLensFigure 25 A came
Page 25 and 26: Goals■ Measure the imagedistance
Page 27 and 28: SOMETIMESGREATDISCOVERIESHAPPEN BYA
Page 29 and 30: concave lens p. 565convex lens p. 5
Page 31 and 32: Record your answers on the answer s

Light Mirrors and Lenses (3379.0K) - McGraw-Hill Higher Education

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