A) 30 cm
B) 10 cm
C) 25 cm
D) 30 cm
Correct Answer: A
Solution :
Here: \[\mu =1.5,{{R}_{1}}=20cm,\,\,{{R}_{2}}=-20cm\] From lens makers formula \[\frac{1}{f}=(\mu -1)\left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right)\] or \[\frac{1}{f}=(1.5-1)\left( \frac{1}{20}-\frac{1}{-20} \right)\] or \[\frac{1}{f}=0.5\times \frac{2}{20}\] or \[f=20cm\]You need to login to perform this action.
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