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♥ ♥ Hey Friends ♥ ♥At what distance from a cancave mirror of focal length 10cm should an object 2cm long be placed in order to get an erect image 6cm tall?.....

Answer»

Concave MIRROR , f is negative ,  f = -10 cm
   u = ?
 h = 2 cm 
 erect image  so  h' is positive,  h' = 6 cm
     so m = h'/h = 3
         as  m = -V/u = 3  => v = -3 u

   mirror equation  is  1/v + 1/u = 1/f

       1/(-3u) + 1/u = 1/(-10)
          2/(3u) = -1/10
            u = -20 /3 cm = -6.67 cm         and  v = -3 u = 20 cm
           v is positive,  so image is behind the mirror and is virtual.

  in concave mirror , an erect image is obtained when the object is between the pole and the FOCUS. it is magnified and is virtual.  so  you can VERIFY from values of u, v and f.


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