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A convex lens of focal length 10 cm. is used as a magnifying lens. Where should the object be placed if the image is to be 30 cm from the lens? |
Answer» Solution : In CASE of magnifying lens, the lens is CONVERGENT and the image is erect, ENLARGED, virtual, between infinity and object and on the same side of lens as shown in FIGURE So here f = 10 cm and v= -30 cm and hence from lens-formula, `(1)/(v )-(1)/(u ) =(1)/(f) ` we have ` (1)/(-30)- (1)/(u)= (1)/(10)` `i.e., u=-7.5cm` So the object must be placed in front of lens at a DISTANCE of 7.5 cm (which is |
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