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Unformatted text preview: 36 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 Image Formation ANSWERS TO QUESTIONS Q36.1 The mirror shown in the textbook picture produces an inverted image. It actually reverses top and bottom. It is not true in the same sense that “Most mirrors reverse left and right.” Mirrors don’t actually flip images side to side—we just assign the labels “left” and “right” to images as if they were real people mimicking us. If you stand face to face with a real person and raise your left hand, then he or she would have to raise his or her right hand to “mirror” your movement. Try this while facing a mirror. For sake of argument, let’s assume you are facing north and wear a watch on your left hand, which is on the western side. If you raise your left hand, you might say that your image raises its right hand, based on the labels we assign to other people. But your image raises its western-side hand, which is the hand with the watch. Q36.2 With a concave spherical mirror, for objects beyond the focal length the image will be real and inverted. For objects inside the focal length, the image will be virtual, upright, and magnified. Try a shaving or makeup mirror as an example. Q36.3 With a convex spherical mirror, all images of real objects are upright, virtual and smaller than the object. As seen in Question 36.2, you only get a change of orientation when you pass the focal point—but the focal point of a convex mirror is on the non-reflecting side! Q36.4 The mirror equation and the magnification equation apply to plane mirrors. A curved mirror is made flat by increasing its radius of curvature without bound, so that its focal length goes to infinity. From 1 1 1 p q f + = = we have 1 1 p q = − ; therefore, p q = − . The virtual image is as far behind the mirror as the object is in front. The magnification is M q p p p = − = = 1. The image is right side up and actual size. Q36.5 Stones at the bottom of a clear stream always appears closer to the surface because light is refracted away from the normal at the surface. Example 36.8 in the textbook shows that its apparent depth is three quarters of its actual depth. 345 346 Image Formation Q36.6 For definiteness, we consider real objects ( p > 0). (a) For M q p = − to be negative, q must be positive. This will happen in 1 1 1 q f p = − if p f > , if the object is farther than the focal point. (b) For M q p = − to be positive, q must be negative. From 1 1 1 q f p = − we need p f < ....
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- Spring '08