A) 40 cm
B) 30 cm
C) 20 cm
D) 10 cm
Correct Answer: C
Solution :
Let distance between lenses be\[x\]. As per the given condition, combination behaves as a plane glass plate, having focal length\[\infty \]. So by using \[\frac{1}{F}=\frac{1}{{{f}_{1}}}+\frac{1}{{{f}_{2}}}-\frac{x}{{{f}_{1}}{{f}_{2}}}\] \[\Rightarrow \] \[\frac{1}{\infty }=\frac{1}{+30}+\frac{1}{-10}-\frac{x}{(+30)(-10)}\Rightarrow x=20\]\[cm\]You need to login to perform this action.
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