A) \[-4.8\,\,cm,\,\,-3.3\,\,D\]
B) \[-5.8\,\,cm,\,\,-4.3\,\,D\]
C) \[-7.5\,\,cm,\,\,-6.3\,\,D\]
D) \[-15.8\,\,cm,\,\,-6.33\,\,D\]
Correct Answer: D
Solution :
The student should use a lens which forms image at distance of \[15\,\,cm\] of the object placed at \[3m\] i.e., object distance \[u=3m=300cm\], image distance From lens formula\[\frac{1}{v}-\frac{1}{u}=\frac{1}{f}\] we get \[\frac{1}{-15}-\frac{1}{-300}=\frac{1}{f}\] or \[\frac{1}{f}=\frac{1}{300}-\frac{1}{15}=-\frac{19}{300}\] or \[f=\frac{-300}{19}\] \[=-15.8\,\,m\] (concave lens) Now power of the lens is \[P=\frac{1}{f}=\frac{1}{-015.8}\]You need to login to perform this action.
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