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The size of the image of an object,which is at infinity, as formed by a convex lens of focal length 20 cm is placed between the convex lens and the image at the distance of 26 cm from the convex lens, the new size of the image is |
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Answer» `1.25` cm `I_(1)` acts as VIRTUAL object for CONCAVE lens. Concave lens forms the image of `I_(1)` at `I_(2)`.  Lens formula : `(1)/(v)-(1)/(u)=(1)/(f)` For concave lens, `(1)/(v)-(1)/(4)=-(1)/(20)` or `(1)/(v)=-(1)/(20)+(1)/(4)=(4)/(20)=(1)/(5)` or v= `5` cm = distance of `I_(2)` from concave lens. `:. " magnification of concave lens" =(v)/(u)=(5)/(4)=1.25` As size of image at `I_(1)` is `2` cm, therefore size of image at `I_(2)xx1.25=2.5` cm |
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