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A spherical mirror gives real image 3 times greater than object. If distance between object and image is 100 cm, then its focal length is |
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Answer» 15 cm `therefore 3=v/u` `therefore 3=v/u` `therefore v=3u` Now u+v=100 `therefore u+3u=100` `therefore 4u=100` `therefore u=25 cm` `therefore` Now m=`(F)/(f-u)` `3=(f)/(f-(-25))` `therefore3 =(f)/(f+25)` therefore 35 -75 =f` `therefore 2F =-75` `therefore f=-37.5` cm |
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