Find focal length of a lens if it produces an image 10cm away
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Here f= 10 cm (positive for convex lens)
m(magnification )=-3 (as image is real it will be inverted)
m=-(V/U) where V is image distance and U is object distance considering sign conventions
-3=-V/U
V=3U
Now using lens formula -1/U+1/V=1/f we get
-1/U+1/3U=1/10
-2/3U=1/10
U=-20/3=-6.66 m
So object is located at distance of 6.66m from the optical centre of lens and is located on left side of it if we consider light ray's travelling from left to right.
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