A) 40 cm
B) 30 cm
C) 20cm
D) 15cm
Correct Answer: B
Solution :
From the formula, \[\frac{1}{f}=\frac{1}{v}-\frac{1}{u}\] we have, \[u=\frac{f(m-1)}{m}\] For virtual image, \[m=+2,\] and for real image, \[m=-2\] \[\therefore \] \[-10=-\frac{f(2-1)}{2}\] (Real object distances are always negative.) \[\Rightarrow \] \[f=20\] For the real image,\[u=\frac{f(-2-1)}{-2}=\frac{-20(-1)}{-2}=30\]You need to login to perform this action.
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