At what distance the object should be placed so that the image will be formed at a distance 10 cm from a concave lens? Focal length of the lens is 20 cm.
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Given distance of image (v)=10cm
focal length(f)=20cm
distance of object(u)=???
1/f = 1/u + 1/v
or 1/20 = 1/u + 1/10
or 1/u = 1/20 - 1/10 = 1-2/20 = -1/20
or u= -20
Since u is negative, it should be placed infront of the mirror at a distance of 20cm
focal length(f)=20cm
distance of object(u)=???
1/f = 1/u + 1/v
or 1/20 = 1/u + 1/10
or 1/u = 1/20 - 1/10 = 1-2/20 = -1/20
or u= -20
Since u is negative, it should be placed infront of the mirror at a distance of 20cm
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1
Answer:
-20
the image formed by concave lens is virtual
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