A) 10 cm
B) 18 cm
C) 30 cm
D) 15 cm
Correct Answer: D
Solution :
For viewing far objects, concave lenses are used and for concave lens u = wants to see = - 30 v = can see = - 10 So from \[\frac{1}{f}=\frac{1}{v}-\frac{1}{u}\] \[\Rightarrow \] \[\frac{1}{f}=\frac{1}{-10}+\frac{1}{30}\] \[\frac{1}{f}=\frac{-3+1}{30}\] \[f=-15\,cm\]You need to login to perform this action.
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