{"id":1351,"date":"2023-03-22T16:50:15","date_gmt":"2023-03-22T16:50:15","guid":{"rendered":"https:\/\/vartmaaninstitutesirsa.com\/?page_id=1351"},"modified":"2023-04-30T07:26:20","modified_gmt":"2023-04-30T07:26:20","slug":"class-10-chapter-9-light-reflection-and-refraction","status":"publish","type":"page","link":"https:\/\/vartmaaninstitutesirsa.com\/index.php\/class-10-chapter-9-light-reflection-and-refraction\/","title":{"rendered":"chapter 9 light reflection and refraction"},"content":{"rendered":"\r\n

UNIT- 9 Light- Reflection and Refraction<\/u><\/strong><\/h1>\r\n\r\n\r\n\r\n

Light Reflection and Refraction <\/strong><\/h2>\r\n\r\n\r\n\r\n

in chapter 9 of 10th class light reflection and refraction we will discuss the phenomenon of light such as reflection and refraction etc.<\/strong><\/p>\r\n\r\n\r\n\r\n

    \r\n
  1. \r\n

    Optics:<\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

    It is that branch of physics which deals with the study of light and phenomenon due to light, such as reflection, refraction, diffraction, interference; desperation, polarization and scattering etc. on the basis of nature of light i.e. ray nature and wave nature.<\/p>\r\n\r\n\r\n\r\n

    Optics may be divided in to two parts: 1. Ray Optics\u00a0 2. Wave Optics<\/p>\r\n\r\n\r\n\r\n

      \r\n
    • Reflection, refraction, dispersion of light can be explained using ray optics.<\/em><\/li>\r\n\r\n\r\n\r\n
    • Polarization, interference, Diffraction, etc can be explained using wave optics<\/em>.<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
        \r\n
      1. \r\n

        Light:<\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

        A form of energy which travel in form of radiations with or without medium and due to which vision process is possible is called light.<\/em><\/p>\r\n\r\n\r\n\r\n

        Form of Light:<\/u><\/p>\r\n\r\n\r\n\r\n

          \r\n
        • Ray of light :-<\/u><\/strong> The path along which light travel from source to receiver called ray of light<\/li>\r\n\r\n\r\n\r\n
        • Pencil of light:<\/u><\/strong> A group of rays starting from a point called pencil of light.<\/li>\r\n\r\n\r\n\r\n
        • Beam of of light<\/u><\/strong>: A collection of ray with well defined boundary called beam of light.<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
            \r\n
          1. \r\n

            Reflection of Light:<\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

            The phenomenon of bending or re-bouncing back of light in the same medium after striking a reflecting surface (mirror) is called reflection of light.<\/u> The vision process is possible only due to reflection of light.<\/p>\r\n\r\n\r\n\r\n

            \"\"<\/figure>\r\n\r\n\r\n\r\n

            \u00a0Laws of Reflection:-imp<\/sup><\/u><\/strong><\/p>\r\n\r\n\r\n\r\n

            1st<\/sup> Law:<\/u><\/em><\/strong> The incident ray, reflected ray and normal to the surface lie in the same plane.<\/p>\r\n\r\n\r\n\r\n

            2nd<\/sup> Law<\/strong>: The angle of incidence is equal to the angle of reflection. \u00a0\u00a0\u00a0<\/p>\r\n\r\n\r\n\r\n

            \u00a0 i.e<\/p>\r\n\r\n\r\n\r\n

            \"\"<\/figure>\r\n\r\n\r\n\r\n
              \r\n
            1. A ray of light incident at an angle 60o<\/sup> .Than what is the angle of reflection?<\/strong><\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

              Ans\u00a0<\/strong>: 60o<\/sup><\/p>\r\n\r\n\r\n\r\n

                \r\n
              1. \r\n

                Real and Virtual images:-<\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

                An image is formed when the light rays coming from an object meet at a point after reflection from a mirror (or refraction from lens).<\/em><\/p>\r\n\r\n\r\n\r\n

                  \r\n
                • The images are of two types<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                  A Real Images<\/u><\/strong>:-<\/em><\/p>\r\n\r\n\r\n\r\n

                  Real images are formed when reflected rays of light coming from an object actually meets at a point after reflection from a mirror. Real images can be formed on a screen and can be seen with the eyes.<\/p>\r\n\r\n\r\n\r\n

                  B Virtual images:-<\/u><\/strong>\u00a0<\/u><\/strong><\/p>\r\n\r\n\r\n\r\n

                  Virtual image are formed when reflected rays of light coming \u00a0from an object actually do not meet but seems to meet at a point after reflection from a mirror. It will appear to meet at a point in or behind the mirror .A plane mirror always forms virtual images.<\/p>\r\n\r\n\r\n\r\n

                  \u00a0\u00a0\u00a0\u00a0 Lateral inversion: –<\/u><\/strong>\u00a0<\/u><\/strong><\/p>\r\n\r\n\r\n\r\n

                  If an object is placed in front of the mirror, then the right side of the object appears to be the left side and left side of the object appears to be the right side of this image. This change of sides of an object and its mirror image is called lateral inversion.<\/p>\r\n\r\n\r\n\r\n

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                  1. \r\n

                    Plane Mirror:\u00a0<\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n

                    A mirror whose reflecting part is plane called plane mirror.<\/em><\/p>\r\n\r\n\r\n\r\n

                    \u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Characteristic of Image Formed by Plane Mirror:<\/u><\/strong><\/p>\r\n\r\n\r\n\r\n

                    \"Image<\/figure>\r\n\r\n\r\n\r\n
                      \r\n
                    • The image formed by plane mirror is of same size to that of object.<\/li>\r\n\r\n\r\n\r\n
                    • The image formed by a plane mirror is at same distance behind the mirror as the object is in front of it.<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
                        \r\n
                      • Image formed by plane mirror is virtual and erect.<\/li>\r\n\r\n\r\n\r\n
                      • The image formed by plane mirror is latterly inverted. i.e<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                        6 Some important facts about the plane mirror.<\/strong><\/h3>\r\n\r\n\r\n\r\n
                          \r\n
                        • If the mirror is rotated at an angle \u03b8 then image rotates at angle 2 \u03b8.<\/li>\r\n\r\n\r\n\r\n
                        • The minimum length of a plane mirror should be equal to half of the height of an object to see full size.<\/li>\r\n\r\n\r\n\r\n
                        • If an object moves toward plane mirror with a speed then image will move toward or away from mirror with speed .<\/li>\r\n\r\n\r\n\r\n
                        • The linear magnification of a plane mirror is 1 and focal length=\u221e and power of plane mirror is O.<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
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                          1. \r\n

                            Spherical Mirrors:<\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

                            A part of spherical reflecting surface is called spherical mirror. These are of two types:<\/p>\r\n\r\n\r\n\r\n

                            \"Spherical<\/figure>\r\n\r\n\r\n\r\n
                              \r\n
                            • Convex Mirror:<\/u><\/strong><\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                              A spherical mirror whose inner part is polished and outer part is reflecting called convex mirror called convex mirror.<\/p>\r\n\r\n\r\n\r\n

                                \r\n
                              • Concave Mirror:<\/u><\/strong><\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                A spherical mirror whose inner part is reflecting and outer part is polished called concave mirror or a mirror whose reflecting part is toward centre called concave mirror.<\/p>\r\n\r\n\r\n\r\n

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                                1. \r\n

                                  Application or Uses of Spherical Mirror: imp<\/sup><\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

                                  Concave Mirror:<\/strong> Dentist, ENT specialist, for saving and make up, in cinema projector, in reflecting type telescope, in solar cooker, in search light, motor head light, in torch, in dish antenna.<\/p>\r\n\r\n\r\n\r\n

                                  Convex Mirror<\/strong>: As rear view mirror, in reflector for street lighting, in big shops to monitor the activities of customers.<\/p>\r\n\r\n\r\n\r\n

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                                  1. \r\n

                                    Some Important Terms Related to Spherical Mirrors:<\/u><\/em><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                    \"Spherical<\/figure>\r\n\r\n\r\n\r\n
                                      \r\n
                                    • Centre of Curvature (C):<\/strong><\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                      The centre of sphere of which the spherical mirror is a part called centre of curvature.<\/p>\r\n\r\n\r\n\r\n

                                        \r\n
                                      • Radius of Curvature (R):<\/strong><\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                        The radius of sphere of which the spherical mirror is a part called radius of curvature.<\/p>\r\n\r\n\r\n\r\n

                                          \r\n
                                        • Pole (Vertex):<\/strong><\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                          The midpoint of the spherical mirror is called pole (P).<\/p>\r\n\r\n\r\n\r\n

                                            \r\n
                                          • Principle Axis:<\/strong><\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                            The line joining the C and P called principle axis.<\/p>\r\n\r\n\r\n\r\n

                                              \r\n
                                            • Aperture:<\/strong><\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                              The effective diameter of the mirror is called aperture.<\/p>\r\n\r\n\r\n\r\n

                                                \r\n
                                              • Focus:<\/strong><\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                                The point on the principle axis at which light after reflection from mirror meets or appears to meat called focus (F).<\/p>\r\n\r\n\r\n\r\n

                                                  \r\n
                                                • Focal Length:<\/strong><\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                                  The distance between pole and focus of a mirror is called focal length (f).<\/p>\r\n\r\n\r\n\r\n

                                                    \r\n
                                                  • Focal length of a spherical mirror is equal to half of radius of curvature of the mirror.<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                                    10.New Cartesian Sign Convention for Spherical Mirrors:-imp<\/sup><\/u><\/strong><\/h3>\r\n\r\n\r\n\r\n
                                                    \"New<\/figure>\r\n\r\n\r\n\r\n
                                                      \r\n
                                                    • All the distances should be measured from the pole of mirror.<\/li>\r\n\r\n\r\n\r\n
                                                    • The distances measured in direction of light are taken positive.<\/li>\r\n\r\n\r\n\r\n
                                                    • The distance measured in oppose to direction of light are taken negative .<\/li>\r\n\r\n\r\n\r\n
                                                    • The distance measured above the principle axis should be taken positive.<\/li>\r\n\r\n\r\n\r\n
                                                    • The distance below the principle axis should be taken negative .<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                                      Rules for tracing images formed by Spherical Mirrors<\/h3>\r\n\r\n\r\n\r\n


                                                      Rule 1: <\/strong>A ray which is parallel to the principal axis after reflection passes through the principal focus in a concave mirror or appears to diverge from the principal focus in a convex mirror.<\/p>\r\n\r\n\r\n\r\n

                                                      \"Rules<\/figure>\r\n\r\n\r\n\r\n

                                                      Rule 2: <\/strong>A ray passing through the principal focus of a concave mirror or a ray which is directed towards the principal focus of a convex mirror emerges parallel to the principal axis after reflection.<\/p>\r\n\r\n\r\n\r\n

                                                      \"Rules<\/figure>\r\n\r\n\r\n\r\n

                                                      Rule 3: <\/strong>A ray passing through the centre of curvature of a concave mirror or directed towards the centre of curvature of a convex mirror is reflected back along the same path.<\/p>\r\n\r\n\r\n\r\n

                                                      \"Rules<\/figure>\r\n\r\n\r\n\r\n


                                                      Rule 4: <\/strong>A ray incident obliquely towards the pole of a concave mirror or a convex mirror is reflected obliquely as per the laws of reflection.<\/p>\r\n\r\n\r\n\r\n

                                                      \"Rules<\/figure>\r\n\r\n\r\n\r\n
                                                        \r\n
                                                      1. \r\n

                                                        Image formed by concave mirror:-<\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                          \r\n
                                                        1. If object is placed at infinite than the image is formed at the focus. The image will be real and inverted and point sized.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                          \"Image<\/figure>\r\n\r\n\r\n\r\n
                                                            \r\n
                                                          1. If object is placed beyond center than the image is formed between center and focus. The image will be real and inverted and smaller in size.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                            \"Image<\/figure>\r\n\r\n\r\n\r\n
                                                              \r\n
                                                            1. If object is placed at centre than the image is also formed at Centre. The image will be real and inverted and of same size as that of object.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                              \"Image<\/figure>\r\n\r\n\r\n\r\n
                                                                \r\n
                                                              1. If object is placed between centre and focus than the image is formed beyond centre. The image will be real and inverted and large sized.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                \"Image<\/figure>\r\n\r\n\r\n\r\n
                                                                  \r\n
                                                                1. If object is placed at focus than the image is formed at infinity. The image will be real and inverted and very large sized.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                  \"Image<\/figure>\r\n\r\n\r\n\r\n
                                                                    \r\n
                                                                  1. If object is placed between pole and focus than the image is formed behind the mirror ce. The image will be virtual and erect.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                    \"Image<\/figure>\r\n\r\n\r\n\r\n
                                                                      \r\n
                                                                    • \r\n

                                                                      Characteristics of images formed<\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
                                                                      \r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
                                                                      Position of object<\/strong><\/td>\r\nPosition of image<\/strong><\/td>\r\nSize of image<\/strong><\/td>\r\nNature of image<\/strong><\/td>\r\n<\/tr>\r\n
                                                                      At infinity<\/td>\r\nAt focus F<\/td>\r\nHighly diminished<\/td>\r\nReal and inverted<\/td>\r\n<\/tr>\r\n
                                                                      Beyond C<\/td>\r\nBetween F and C<\/td>\r\nDiminished<\/td>\r\nReal and inverted<\/td>\r\n<\/tr>\r\n
                                                                      At C<\/td>\r\nAt C<\/td>\r\nEqual to size of object<\/td>\r\nReal and inverted<\/td>\r\n<\/tr>\r\n
                                                                      Between C and F<\/td>\r\nBeyond C<\/td>\r\nEnlarged<\/td>\r\nReal and inverted<\/td>\r\n<\/tr>\r\n
                                                                      At F<\/td>\r\nAt infinity<\/td>\r\nHighly enlarged<\/td>\r\nReal and inverted<\/td>\r\n<\/tr>\r\n
                                                                      Between F and P<\/td>\r\nBehind the mirror<\/td>\r\nEnlarged<\/td>\r\nVirtual and erect<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/figure>\r\n\r\n\r\n\r\n

                                                                      12\u00a0 Image formed by convex mirror:- <\/u><\/strong><\/h3>\r\n\r\n\r\n\r\n
                                                                        \r\n
                                                                      1. If object is placed at infinity than image will form at focus. The image will be highly diminished point sized, the image will be virtual and erect.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                        \"Image<\/figure>\r\n\r\n\r\n\r\n
                                                                          \r\n
                                                                        1. If object is placed between pole and infinity than image will form between pole and focus. The image will be virtual and erect and diminished<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                          \"Image<\/figure>\r\n\r\n\r\n\r\n

                                                                          13 .Mirror Formula or Mirror Equation: imp<\/sup><\/u><\/strong><\/h3>\r\n\r\n\r\n\r\n

                                                                          A relation between position of object u, position of image v and focal length f of a mirror is called mirror formula<\/em><\/p>\r\n\r\n\r\n\r\n

                                                                          \"\"<\/figure>\r\n\r\n\r\n\r\n

                                                                          14 \u00a0Linear Magnification of Mirror (<\/u><\/strong> m):<\/u><\/strong> imp<\/sup><\/u><\/strong><\/h3>\r\n\r\n\r\n\r\n

                                                                          It is defiened as the ratio of height of the image to the height of the object<\/p>\r\n\r\n\r\n\r\n

                                                                          i.e\u00a0 \u00a0\"Linear<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          If <\/em> m<1\u00a0then image will be smaller then obect<\/em><\/p>\r\n\r\n\r\n\r\n

                                                                          If <\/em> m>\u00a0then image will be larger then object.<\/em><\/p>\r\n\r\n\r\n\r\n

                                                                          If <\/em>m=1 \u00a0then size of image will be equal to size of obejct (plane mirror)<\/em><\/p>\r\n\r\n\r\n\r\n

                                                                          If <\/em>m is positive \u00a0image will be real and if <\/em>m is negative image will be virtual.<\/em><\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          Example 2 An object, 4.0 cm in size, is placed at 25.0 cm in front of a concave mirror of focal length 15.0 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and the size of the image.<\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                          \"An<\/figure>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          Question3: <\/em>An object is placed in front of a concave mirror at a distance of 7.5 cm from it. If the real<\/strong> Image is formed at a distance of 30 cm from the mirror, find the focal Length of the mirror. What<\/strong> Would be the focal? Length if the image is virtual? <\/strong>\u00a0 \u00a0 \u00a0 Solution: <\/em>Case I: <\/strong>When the image is real. We have u = \u2013 7.5 cm; v <\/em>= \u2013 30 cm ; f<\/em> = ?\u00a0<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          \"An<\/figure>\r\n\r\n\r\n\r\n

                                                                          \u00a0Case II: <\/strong>When the image is virtual: In this case, u<\/em> = \u2013 7.5 cm v = + 30 cm\u00a0<\/p>\r\n\r\n\r\n\r\n

                                                                          We know\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"\"<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          Question4: <\/em><\/strong>An object 5 mm high is placed 30 cm from a convex mirror whose focal length is 20 cm. Find the position (in cm), size (in mm) and nature of the image.\u00a0\u00a0 <\/strong>\u00a0\u00a0\u00a0<\/p>\r\n\r\n\r\n\r\n

                                                                          Solution: \u00a0\u00a0\u00a0<\/em><\/strong>We have,\u00a0 u<\/em> = \u2013 30 cm ; v<\/em> = ? f<\/em> = + 20 cm<\/p>\r\n\r\n\r\n\r\n

                                                                          \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 We know\u00a0 \u00a0\u00a0\"An<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          The image is formed 12 cm behind the mirror, it is virtual.<\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                          \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Now, \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"\"<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          Hence the height of the image = 2mm<\/strong> the positive sign indicates that the image is erect.<\/p>\r\n\r\n\r\n\r\n

                                                                          Question5: <\/em><\/strong>An object 2 mm high is placed 150 mm from a concave mirror of focal length 5 cm. Find the position (in mm) and size (in mm) of the image.\u00a0\u00a0\u00a0 <\/strong>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\"An<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          Question 6.<\/strong>\u00a0 A small candle, 2.5 cm in size is placed at 27 cm in front of a concave mirror of radius of curvature 36 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Describe the nature and size of the image. If the candle is moved closer to the mirror, how would screen have is moved?
                                                                          <\/strong>Solution: <\/strong>\u00a0The object is kept between \u0192 and C. So the image should be real, inverted and beyond C. To locate the sharp image, screen should be placed at the position of image.<\/p>\r\n\r\n\r\n\r\n

                                                                          \"A<\/figure>\r\n\r\n\r\n\r\n

                                                                          So, the image is inverted and magnified. Thus in order to locate the sharp image, the screen should be kept 54 cm in front of concave mirror and image on the screen will be observed real, inverted and magnified. If the candle is moved closer to the mirror, the real image will move away from the mirror, hence screen has to be shifted away from the mirror to locate the sharp image.<\/p>\r\n\r\n\r\n\r\n

                                                                          \u00a0Question 7<\/strong>:\u00a0 A 4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the location of the image and the magnification. Describe what happens as the needle is moved farther from the mirror.<\/strong>
                                                                          Solution:<\/strong> A convex mirror always form virtual image, which is erect and small in size of an object kept in front of it. Focal length of convex mirror \u0192 = + 15 cm Object distance u = \u2013 12 cm.<\/p>\r\n\r\n\r\n\r\n

                                                                          \u00a0Using mirror formula\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"A<\/p>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          Therefore, image is virtual, formed at 6.67 cm at the back of the mirror.<\/p>\r\n\r\n\r\n\r\n

                                                                          Magnification\u00a0 \u00a0\"\" so size of the image I= (m\u00d7O) =2.5 cm
                                                                          It shows the image is erect, small in size and virtual. When the needle is moved farther from mirror the image also move towards focus and decreasing in size. As u approaches v approaches focus but never beyond \u0192.<\/p>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          Example:8 \u00a06 A convex mirrors used for rear-view on an automobile has a radius of curvature of 3 m. If a bus is located at 5 m from this mirror, find the position, nature and size of the image.<\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                          Solution Radius of curvature, R = + 3 m;<\/p>\r\n\r\n\r\n\r\n

                                                                          Object-distance, u = \u2013 5 m;\u00a0 Image-distance, v = ?\u00a0 Height of the image, h\u2032= ?<\/p>\r\n\r\n\r\n\r\n

                                                                          \"\u00a06<\/figure>\r\n\r\n\r\n\r\n

                                                                          Example 8: \u00a0an object, 4.0 cm in size, is placed at 25.0 cm in front of a concave mirror of focal length 15.0 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and the size of the image.<\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                          Solution Object-size, h = + 4.0 cm;\u00a0\u00a0\u00a0 u = \u2013 25.0 cm;\u00a0\u00a0 f = \u201315.0 cm; Image-distance,\u00a0\u00a0 v =?\u00a0 Image-size, h\u2032 =?<\/p>\r\n\r\n\r\n\r\n

                                                                          From Eq.\u00a0 \"an<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          The screen should be placed at 37.5 cm in front of the mirror. The image is real.<\/p>\r\n\r\n\r\n\r\n

                                                                          Also, magnification,\u00a0 \u00a0\"\"<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                          Height of the image, h\u2032 = \u2013 6.0 cm the image is inverted and enlarged.<\/p>\r\n\r\n\r\n\r\n

                                                                          Question9: Find the focal length of a convex mirror whose radius of curvature is 32 cm.<\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                          Question10: A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front of it. Where is the image located?<\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                          15 Reflecting of Light:<\/u><\/strong><\/h3>\r\n\r\n\r\n\r\n

                                                                          The phenomenon of the change in the path of light when it moves from one medium to another medium is called refraction of light.<\/em><\/p>\r\n\r\n\r\n\r\n

                                                                          \"Reflecting<\/figure>\r\n\r\n\r\n\r\n

                                                                          Refraction of light occurs because light changes its velocity when it moves from one medium to another medium. On refraction both velocity and wavelength of light changes but frequency remains unchanged.<\/u><\/em><\/p>\r\n\r\n\r\n\r\n

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                                                                          1. \r\n

                                                                            Laws of Refraction of Light: imp<\/sup><\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

                                                                            \u00a0\u00a0 (i)\u00a0 <\/strong>The incident ray, refracted ray and normal to the surface meet at a point.<\/p>\r\n\r\n\r\n\r\n

                                                                            \u00a0\u00a0 (ii)\u00a0 Snell\u2019s Law:<\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                            The ratio of sine of angle of incidence to the sine of angle of refraction is constant for a pair of media.<\/p>\r\n\r\n\r\n\r\n

                                                                            i.e\"\"<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                            Here \"\" \u00a0is called refractive index of second media w.r.t first medium.<\/p>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n

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                                                                            1. \r\n

                                                                              Refractive Index: or Absolute Refraction Index: imp<\/sup><\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

                                                                              The ratio of velocity of light in vacuum to the velocity of light in a medium is called absolute refractive index or simply refractive index<\/p>\r\n\r\n\r\n\r\n

                                                                              i.e\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\"\"<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                              \u00a0Absolute refractive index may not be less than one because<\/em> always c>v .<\/em><\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                              Relative Refraction Index:<\/u><\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                              Suppose there are two medium of refractive index n1<\/sub>\u00a0and n2<\/sub> \u00a0then 1<\/sup>n2<\/sub>\u00a0called relative refractive of two w.r.t one.<\/p>\r\n\r\n\r\n\r\n

                                                                              \"\"<\/figure>\r\n\r\n\r\n\r\n
                                                                                \r\n
                                                                              • Clearly smaller, the refractive index of a medium larger the velocity of light in that medium.<\/em><\/li>\r\n\r\n\r\n\r\n
                                                                              • Refractive indexes are a scalar quantity and have no units.<\/em><\/li>\r\n\r\n\r\n\r\n
                                                                              • A medium having higher refraction index called optical denser medium and a medium <\/em>having lower refraction index called rare medium.<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                                                                Question11: \u00a0\u00a0 <\/em>If wavelength of light in glass is 7200 \u00c5, then find the wavelength of same light (in \u00c5) in water. (n<\/strong>w<\/sub> = 4\/3, n<\/strong>g<\/sub> = 3\/2)<\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                                Solution: \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0<\/em><\/strong>\"\"<\/p>\r\n\r\n\r\n\r\n\r\n\r\n

                                                                                Question 12: <\/strong>\u00a0the refractive index of glass is 1.5. What is the speed of light in glass?<\/strong> \u00a0<\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                                \"\"<\/figure>\r\n\r\n\r\n\r\n
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                                                                                1. \r\n

                                                                                  Principle of Reversibility of Light (Refraction through a Glass Slab): imp<\/sup><\/u><\/strong><\/h3>\r\n<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n

                                                                                  Suppose a ray of light PQ incident at Q point on a glass slab as shown in fig.<\/p>\r\n\r\n\r\n\r\n

                                                                                  \"Principle<\/figure>\r\n\r\n\r\n\r\n
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                                                                                  • We can see that when a mirror is placed <\/em>\u22a5<\/em> to the path of light, then light regain its original path. This phenomenon is called principle of reversibility of light.<\/strong><\/em><\/li>\r\n\r\n\r\n\r\n
                                                                                  • The perpendicular distance between incident ray and emergent ray is called lateral shift. In above fig. d is the lateral shift.<\/em><\/li>\r\n\r\n\r\n\r\n
                                                                                  • Lateral shift increase with thickness of glass slab, increase in incidence angle and refractive index of glass slab.<\/em><\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n

                                                                                    19.Lens:<\/u><\/strong><\/h3>\r\n

                                                                                    A lens is piece of transparent material bounded by two refracting surfaces out of which at least one is curved. Various types of lenses are as given below:<\/p>\r\n\r\n\r\n\r\n

                                                                                    \"\"<\/figure>\r\n\r\n\r\n\r\n

                                                                                    Uses:<\/u><\/em><\/strong> lenses are commonly used to correct vision deflects in human eyes. They are also used in microscopes, telescopes and cameras, cinemas, photography.<\/p>\r\n\r\n\r\n\r\n

                                                                                    Terms Used in Lenses:<\/u><\/em><\/strong><\/p>\r\n\r\n\r\n\r\n

                                                                                    Optical Centre:<\/em><\/strong> The point in the lens through which the light passes un-deviated.<\/p>\r\n\r\n\r\n\r\n

                                                                                    Principle Focus (F):<\/em><\/strong> The point on the principle axis on which the rays parallel to principle axis after refraction meats or appear to meet.<\/p>\r\n\r\n\r\n\r\n

                                                                                    20 Convex lens:- <\/u><\/strong><\/h3>\r\n\r\n\r\n\r\n

                                                                                    A transparent medium bounded by two refracting surface which is thicker at the midpoint and thin at the ends called convex lens.<\/p>\r\n\r\n\r\n\r\n

                                                                                    \u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 27. Rules for tracing images formed by spherical lens<\/h2>\r\n\r\n\r\n\r\n

                                                                                    Rule 1: <\/strong>A ray which is parallel to the principal axis, after refraction passes through the principal focus in case of a convex lens or appears to diverge from the principal focus on the same side of the lens in a concave lens.<\/p>\r\n\r\n\r\n\r\n

                                                                                    \"Rules<\/figure>\r\n\r\n\r\n\r\n


                                                                                    Rule 2: <\/strong>A ray passing through the principal focus of a convex lens or appearing to meet at the principal focus of a concave lens after refraction emerges parallel to the principal axis.<\/p>\r\n\r\n\r\n\r\n

                                                                                    \"Rules<\/figure>\r\n\r\n\r\n\r\n

                                                                                    Rule 3: <\/strong>A ray passing through the optical centre of a convex lens or a concave lens emerges without any deviation.<\/p>\r\n\r\n\r\n\r\n

                                                                                    \"Rules<\/figure>\r\n\r\n\r\n\r\n

                                                                                    \u00a0<\/h3>\r\n\r\n\r\n\r\n

                                                                                    Convex lens makes six images <\/u><\/p>\r\n\r\n\r\n\r\n

                                                                                      \r\n
                                                                                    1. If object is placed at infinite than the image is formed at the focus . The image will be real and inverted and point sized.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                                      \"If<\/figure>\r\n

                                                                                      \u00a0<\/h3>\r\n

                                                                                      Image formed by convex lens:-<\/u><\/strong><\/h3>\r\n
                                                                                        \r\n
                                                                                      1. If object is placed beyond Centre of curvature than the image is formed between focus \u00a0and centre . The image will be real and inverted and smaller in size.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                                        \"Rules<\/figure>\r\n\r\n\r\n\r\n
                                                                                          \r\n
                                                                                        1. If object is placed 2F1<\/sub> at than the image is formed at 2F2<\/sub>. The image will be real and inverted and of same size as that of object.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                                          \"Image<\/figure>\r\n\r\n\r\n\r\n
                                                                                            \r\n
                                                                                          1. If object is placed between 2F1<\/sub> and F1<\/sub>\u00a0than the image is formed beyond2F2<\/sub> . The image will be real and inverted and large sized.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                                            \"Image<\/figure>\r\n\r\n\r\n\r\n
                                                                                              \r\n
                                                                                            1. If object is placed at F1<\/sub> than the image is formed at infinity. The image will be real and inverted and very large sized.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                                              \"light<\/figure>\r\n\r\n\r\n\r\n
                                                                                                \r\n
                                                                                              1. If object is placed between pole and Centre than the image is formed behind the lens. The image will be virtual and erect.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
                                                                                                \"Image<\/figure>\r\n\r\n\r\n\r\n