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and Principal

VIEWS: 4 PAGES: 28

  • pg 1
									Images Formed by a
  Concave Mirror



            VII std Science
            (State Syllabus)
     Project Done by:



    B. Dhandapani
     Teacher Educator
  Block Resource Centre
  Sarva Shiksha Abhiyan
    Mannargudi Block
    Thiruvarur District
        Tamil Nadu
Email bdpani@rediffmail.com
To understand the basic principles of
Ray optics

To understand the principles of
“Construction” of ray diagrams

To explain how the images are
formed by the concave mirrors for
various positions of objects
Basic Principles
Terms Used in Concave Mirrors
Construction - Title
Construction 1
Construction 2
Construction 3
Images Formed - Title
Object at Infinity
Object beyond ‘C’
                             Click on the headings to
Object at ‘C’
                             study the relevant topic
Object between ‘F’ and ‘C’
Object at ‘F’
Object between ‘P’ and ‘F’
All in One
Relative Movement of the Object and the Image
Ready Reckonor
Uses of Concave Mirrors
Test Your Understanding
        Spherical Mirrors are Portions of
        spherical surfaces
        If the outside of the spherical mirror is
        silvered, then it is called a concave
        mirror




                               Concave Mirror
Index
   Terms Used in Spherical Mirrors


         Pole (P)                           (C) Centre of Curvature
        Geometrical                               Centre of the
        Centre                                    sphere of which the
                                                  mirror is a part


                    The Line Passing through C,P – Principal Axis



                        P – Pole
                        C – Centre of Curvature
Index                   Principal Axis
Index
              Construction 1

                                    Ray Parallel to Principal Axis



                      F             Principal Axis




        Rule 1. The Ray Parallel to Principal Axis is
        reflected through the Principal Focus ‘F’

Index
                Construction 2



                        F             Principal Axis


                                 Ray Passing through ‘F’


        Rule 2. Ray Passing through the principal focus ‘F’
        is reflected parallel to the Principal Axis .

Index
                Construction 3



                       F         C           Principal Axis




        Rule 3. The ray passing through the Centre of
        Curvature ‘C’ is reflected through the same path.
Index
Index
                       F          C




    All the Rays of the Object at infinity are parallel to Principal
    Axis and hence according to Construction 1 the image is
    formed at ‘F’.



Index
                                            1



                               F           C

                                2




        There are two rays emerging from the object which is placed
        beyond ‘C’. One ray is parallel to Principal Axis and the other
        ray passes through ‘C’. Both the rays meet at the point
        between ‘F’ and ‘C’ where the image is formed.


Index
                                  1


                                      2

                              F           C




        There are two rays emerging from the object which is
        placed at ‘C’. One ray is parallel to Principal Axis and
        the other ray passes through ‘F’. Both the rays meet at
        the point ‘C’ where the image is formed

Index
                                  2
                       1



                           F             C




        There are two rays emerging from the object which is placed
        between ‘F’ and ‘C’. One ray is parallel to Principal Axis and
        the other ray passes through ‘C’. Both the rays meet at the
        point beyond ‘C’ where the image is formed.


Index
                           2
            1

                     F          C




        There are two rays emerging from the object which is
        placed at ‘F’. One ray is parallel to Principal Axis and the
        other ray passes through ‘C’. Both the rays meet at the
        point of infinity.

Index
                                            1

                                                 2

                            P         F              C




        There are two rays emerging from the object which is placed
        between ‘P’ and ‘F’. One ray is parallel to Principal Axis and the
        other ray passes through ‘C’. Both the rays meet at the back of
        the mirror when the rays are extended. The virtual image is
        formed at the back of the mirror.

Index
         …All in One (Recap)
    Object @ Infinity – Image @ ‘F’ – Real, Inverted
Object beyond ‘C’ – Image between ‘F’ & ‘C’- Real, Inverted

                                               Object



           P                                            Infinity

                     F         C

                     Image

       Object @ ‘C’ – Image @ ‘C’ – Real, Inverted.
Object between ‘F’ & ‘C’ – Image beyond ‘C’ – Real, Inverted


 Index
                                              Object



                        Image


When the Object moves closer to the Mirror,

The Image Moves away from the Mirror
                                                  Index
 Index
SlNo      Place of       Place of the         Rays to be Drawn      Nature of the
         the Object     Image Formed                                   Image

                                           All Rays Parallel to     Real, Inverted,
 1       At Infinity   At ‘F’              Principal Axis (PA)      Small

                                           Ray 1 Parallel to PA &   Real, Inverted,
 2       Beyond ‘C’    Between ‘F’ & ‘C’   Ray 2 Through ‘C’        Small

                                           Ray 1 Parallel to PA &   Real, Inverted,
 3       At ‘C’        At ‘C’              Ray 2 Through ‘F’        Same as
                                                                    Object

                                           Ray 1 Parallel to PA &
 4       Between ‘F’   Beyond ‘C’          Ray 2 Through ‘C’        Real, Inverted,
         & ‘C’                                                      Large

                                           Ray 1 Parallel to PA &
 5       At ‘F’        At Infinity         Ray 2 Through ‘C’               --

                       At the Back of      Ray 1 Parallel to PA &   Virtual, Large,
 6       Between ‘F’   the Mirror          Ray 2 Through ‘C’        Straight
         & ‘C’
    Used in mirror telescopes
    (its front is a silver-plated mirror)




                                            •Used in search light, car lights
                                             and telegraphic intermittent lights.

•The spherical concave mirror finds its
most valuable application as eye mirror
(Helmholtz 1851). It serves during               Click on
examination of the inside of eyes.
                                                 pictures to
                                                 get notes
    Index
        Click on    Boxes near the answers and
        know whether Your Answer is Correct or
        needs correction
        Click- For Correct Answer You will hear
        Click -For the incorrect answer You will
        hear



Index
1 Spherical Mirrors are Portions of

  Plain Surfaces                 Spherical Surfaces

  Rough Surfaces                 None


2. Concave Mirrors have the silvered surfaces on the


  Outer Side                      Inner Side

  Both the Sides                  Top Side

                                               Index
3. The geometrical centre of the concave mirror is

      Radius                        Pole


      Focus
                                    Plane



4. Centre of the sphere of which the mirror is a part
is called

       Pole                         Radius of Curvature



      Centre of Curvature           Principal Focus

                                                      Index
 5. The line passing through ‘Centre of Curvature’ and
    ‘Pole’ is known as
       Radius of Curvature              Principal Focus



       Principal Axis                   None



6. The Ray Parallel to Principal Axis ‘P’ is reflected through



         The 2f                          Principal Focus ‘F’


         Between ‘F’ and ‘2f’            None

                                                          Index
 7. The line passing through ‘Principal Focus’ is
    reflected

    Through ‘F’ itself            Through ‘C’



    Parallel to Principal Axis    Through Principal Axis itself




8. The line passing through ‘C’ is reflected 24


    Through ‘C’ itself            Through ‘F’


    Parallel to Principal Axis    On the Principal Axis
                                                      Index
  9. When the object is between ‘F’ and ‘C’, the image is



      Formed at ‘C’               Formed at infinity


     Formed at ‘F’                Formed Beyond ‘C’




10. The image is formed at infinity when the object is


     At ‘P’                      At ‘C’


     At ‘F’                      Between ‘F’ and ‘C’
                                                       Index

								
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