Positions of Object and Image in Concave Mirror
   Position of Object                Position of Image          Size of Image            Nature of Image
   At infinity                       At focus                   Highly diminished        Real and inverted
   Between infinity and C            Between F and C            Dminished                Real and inverted
   At C                              At C                       Same size                Real and inverted
   Between C and F                   Beyond C                   Enlarged                 Real and inverted
   At F                              At infinity                Highly enlarged          Real and inverted
   Between F and P                   Behind mirror              Enlarged                 Virtual and erect
                              Positions and Nature of Image in Convex Mirror
   Position of Object       Position of Image                Size of Image       Nature of Image
   At infinity              At F, behind mirror              Highly diminished Virtual and erect
   Between infinity and P   Between F and P, behind mirror Diminished            Virtual and erect
Where F is focus, P is pole and C is the centre of curvature.
Uses of Mirrors
    Plane mirror            : looking glass,
     constructing periscope, solar cookers,
     kaleidoscope, measuring instruments
    Concave Mirror : headlights of cars,
     dentist"s mirror, solar devices, reflecting
     telescopes, satellite dishes, flash-lights,          Total Internal Reflection
     electron microscopes, etc.
    Convex mirror : street lamps, real view              It occurs when light attempts to move from a
     mirror, etc.                                         medium having a given refractive index to a
                                                          medium having a lower refractive index.
Refraction
    It is the bending of a wave when it enters a
     medium where its speed is different.
    The refraction of light when it passes from
     a fast medium to a slow medium bends the
     light ray toward the normal to the
     boundary between the two media.
Snell"s law or Laws of Refraction                         When light is incident upon a medium of
                                                          lesser index of refraction, the ray is bent away
It states that for a given pair of media and a
                                                          from the normal, so the exit angle is greater
wave with a single frequency, the ratio of the
                                                          than the incident angle. Such reflection is
sines of the angle of incidence θ1 and angle of
                                                          commonly called "internal reflection". The
refraction θ2 is equivalent to the ratio of phase
                                                          exit angle will then approach 90° for some
velocities (v1 / v2) in the two media, or
                                                          critical incident angle θc, and for incident
equivalently, to the opposite ratio of the
                                                          angles greater than the critical angle there will
indices of refraction (n2 / n1):
                                                          be total internal reflection.
           sin 1   v  n
                   1  2                                 e.g. air bubbles in glass paper weight appears
           sin 2  v 2 n1
                                                          silvery white, Sparkling of diamond, etc.
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