A) \[{{R}_{1}}<{{R}_{2}}\]
B) \[{{R}_{1}}>{{R}_{2}}\]
C) \[{{R}_{1}}={{R}_{2}}\]
D) None of these
Correct Answer: A
Solution :
Focal length \[\frac{1}{f}=(\mu -1)\left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right)\] For lens to be concave \[\left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right)>0\] \[\Rightarrow \] \[\frac{1}{{{R}_{1}}}>\frac{1}{{{R}_{2}}}\] \[\Rightarrow \] \[{{R}_{1}}>{{R}_{2}}\]
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