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Class 9 Science Chapter 11 Reflection of Light, , Textbook Questions and Answers, , 1. Answer the following questions., , a. Explain the difference between a plane mirror,, a concave mirror and a convex mirror with, respect to the type and size of the images, produced., , Answer:, , Plane Concave mirror Convex, , mirror mirror, , Type Virtual Virtual (erect) Virtual and, of and as well as Real Erect, , image _ Erect (inverted), , Size of Same Diminished, Diminished, image _ size Same size and, , magnified

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b. Describe the positions of the source of light, with respect to a concave mirror in, , 1. Torch light, , 2. Projector lamp, , 3. Floodlight, , Answer:, , (a) Torch light: The source of light is placed at, the focus., , (b) Projector lamp : The source of light is placed, at the centre of curvature., , (c) Flood light : The source of light is placed just, , beyond the centre of curvature.

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2. What sign conventions are used for reflection, from a spherical mirror?, , Answer:, , According to the Cartesian sign convention, the, pole of the mirror is taken as the origin. The, principal axis is taken as the X-axis of the frame, of reference. The sign conventions are as, , follows., , 1. The object is always kept on the left of, the mirror. All distances parallel to the, principal axis are measured from the pole, of the mirror., , 2. All distances measured towards the right, of the pole are taken to be positive, while, those measured towards the left are, taken to be negative., , 3. The distance measured vertically, upwards from the principal axis are taken, to be positive., , 4. The distance measured vertically, downwards from the principal axis are, taken to be negative., , 5. The focal length of a concave mirror is, negative while that of a convex mirror is, , positive.

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c. Why are concave mirrors used in solar, , devices?, , Answer:, , ° Solar devices like solar cooker or solar, water heater use solar energy to cook, , food or heat water., , e When sun rays fall on the concave mirror,, they converge and come together in the, focal plane., , e Due to convergence, the intensity of sun, rays increases and the food or water is, heated faster. Hence, concave mirrors are, , used in solar- devices.

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d. Why are the mirrors fitted on the outside of, cars convex?, , Answer:, , ¢ Aconvex mirror is used as rear view, mirror because they form erect, virtual,, and diminished images., , * This, allows the driver to view a large area, , in a small mirror., , e. Why does obtaining the image of the sun ona, Paper with the help of a concave mirror burn the, paper?, , Answer:, , e When sunrays fall on the concave mirror,, they converge and come together in the, focal plane., , ¢ Due to convergence, the intensity of, sunrays increases., , * Hence, image of the sun ona paper with, the help of concave mirror bums the, , paper.