A) 25
B) 15
C) 30
D) 50
Correct Answer: B
Solution :
From the figure, \[d={{f}_{1}}-{{f}_{2}}\] Mathematically, \[\frac{1}{{{f}_{1}}}+\frac{1}{{{f}_{2}}}-\frac{d}{{{f}_{1}}{{f}_{2}}}=\frac{1}{F}\] For the emergent beam to be parallel,\[P=0,\,\,F=\propto \] \[\therefore \] \[\frac{1}{20}-\frac{1}{5}+\frac{d}{100}=0\] \[\Rightarrow \] \[d=15\]You need to login to perform this action.
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