A) \[30\,cm\]
B) \[60\,cm\]
C) \[15\,cm\]
D) \[90\,cm\]
Correct Answer: D
Solution :
The image formation by a convex lens is as follows: Image formed is diminished, when object lies between 2F and infinity. Magnification \[(M)=\frac{image\,size}{object\,size}\] \[=\frac{1}{2}=\frac{v}{u}\] ?.(i) From lens formula, \[\frac{1}{f}=\frac{1}{v}-\frac{1}{u}\] ?.(ii) where / is focal length, v the image distance and u the object distance. From Eqs. (i) and (ii), we get \[\frac{1}{f}=\frac{1}{u}+\frac{2}{u}\] Given, \[u=90\text{ }cm\] \[\therefore \] \[\frac{1}{30}=\frac{3}{u}\] \[\Rightarrow \] s\[u=90cm\]You need to login to perform this action.
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