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A 4.5cm needle is placed 12cm away from a convex mirror of focal length 15cm. Given the location of the image and the magniftication. |
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Answer» `6.7cm, 5//9` (focal length of convex mirror is taken as positive) DISTANCE of OBJECT `u=-12cm` Size of object `O=4.5cm` using the mirror formula `1/f=1/v+1/u` `1/15=1/v-1/12` `implies1/v=1/15+1/12=(4+5)/60=9/60` Distance of image from the mirror `v=6.7cm` The positive sign SHOWS that the image is formed behind the mirror. Using the formula of magnification, `m=-v/u=L/O` `(-6.7)/(-12)=l/4.5` Size of image `l=2.5cm` As `l` is positive so image is erect and virtual. Magnification `m` is given by `m=l/O=2.5/4.5=25/45=5/9` |
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