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An object is placed at a distance of 20 cm from a concave mirror . The image is doubled the size of the object and is inverted . Find the focal lenght of the mirror and the position where the image is formed....... ( HINT : ANSWER IS 16 CM .. 48 CM ) ​

Answer»

u= -20 CM,v=?let object's size be x cm,then, image's size be -2x.Now, MAGNIFICATION= hi/ho= -2x/x= -2Again, magnification= -v/u-v/-30=-2v= -60cm.Now, by mirror formula,1/v+1/u=1/f-1/60+(-1)/30=1/fthis IMPLIES, f = -20cm



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