36 - Image Formation

36 - Image Formation - Chapter 36 Image Formation CHAPTE R...

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Chapter 36 Image Formation CHAPTER OUTLINE 36.1 Images Formed by Flat Mirrors 36.2 Images Formed by Spherical Mirrors 36.3 Images Formed by Refraction 36.4 Thin Lenses 36.5 Lens Aberrations 36.6 The Camera 36.7 The Eye 36.8 The Simple Magniﬁer 36.9 The Compound Microscope 36.10 The Telescope 1126 ± The light rays coming from the leaves in the background of this scene did not form a focused image on the ﬁlm of the camera that took this photograph. Consequently, the back- ground appears very blurry. Light rays passing though the raindrop, however, have been altered so as to form a focused image of the background leaves on the ﬁlm. In this chapter, we investigate the formation of images as light rays reﬂect from mirrors and refract through lenses. (Don Hammond/CORBIS)

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1127 T his chapter is concerned with the images that result when light rays encounter ﬂat and curved surfaces. We ﬁnd that images can be formed either by reﬂection or by refraction and that we can design mirrors and lenses to form images with desired char- acteristics. We continue to use the ray approximation and to assume that light travels in straight lines. Both of these steps lead to valid predictions in the ﬁeld called geometric optics. In subsequent chapters, we shall concern ourselves with interference and diffrac- tion effects—the objects of study in the ﬁeld of wave optics. 36.1 Images Formed by Flat Mirrors We begin by considering the simplest possible mirror, the flat mirror. Consider a point source of light placed at O in Figure 36.1, a distance p in front of a flat mirror. The distance p is called the object distance. Light rays leave the source and are reflected from the mirror. Upon reflection, the rays continue to diverge (spread apart). The dashed lines in Figure 36.1 are extensions of the diverging rays back to a point of intersection at I . The diverging rays appear to the viewer to come from the point I behind the mirror. Point I is called the image of the object at O . Regardless of the system under study, we always locate images by extending diverging rays back to a point at which they intersect. Images are located either at a point from which rays of light actually diverge or at a point from which they appear to diverge. Because the rays in Figure 36.1 appear to originate at I , which is a distance q behind the mirror, this is the location of the image. The distance q is called the image distance. Images are classiﬁed as real or virtual. A real image is formed when light rays pass through and diverge from the image point; a virtual image is formed when the light rays do not pass through the image point but only appear to diverge from that point. The image formed by the mirror in Figure 36.1 is virtual. The image of an object seen in a ﬂat mirror is always virtual. Real images can be displayed on a Mirror OI q p Figure 36.1 An image formed by reﬂection from a ﬂat mirror. The image point I is located behind the mirror a perpendicular distance q from the mirror (the image distance). The image distance has the same magnitude as the object distance p .
screen (as at a movie), but virtual images cannot be displayed on a screen. We shall see

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36 - Image Formation - Chapter 36 Image Formation CHAPTE R...

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