A) \[-20cm\]
B) \[40cm\]
C) \[20cm\]
D) \[-40cm\]
Correct Answer: C
Solution :
The focal length of the convex lens is given by \[F=\frac{1}{p}m=\frac{100}{p}cm\] Here, \[p=5D\] \[\Rightarrow \] \[F=\frac{1}{5}\times 100\,cm\] \[\Rightarrow \] \[F=20\,cm\] ?..(i) From formula, \[\frac{1}{\upsilon }=\frac{1}{u}+\frac{1}{f}\] ..?..(ii) Here, \[u=-10\,cm\] and using \[f=20cm,\]then from equation (ii) \[\Rightarrow \] \[\frac{1}{\upsilon }=\frac{1}{-10}+\frac{1}{20}\] \[\Rightarrow \] \[\frac{1}{\upsilon }=\frac{-2+1}{20}=\frac{-1}{20}\] \[\Rightarrow \] \[\upsilon =-20\,cm\] Cecarly the image will be formed at a distance of 20cm on the same side of the object.
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