A) 5 cm
B) 10 cm
C) 20cm
D) 40cm
Correct Answer: A
Solution :
Here, \[u=-20cm,\text{ }v=12+12-20=4cm\] \[\therefore \] \[\frac{1}{f}=\frac{1}{v}+\frac{1}{u}=\frac{1}{4}-\frac{1}{20}\] \[=\frac{5-1}{20}\] \[=\frac{4}{20}=\frac{1}{5}\] \[\therefore \] \[f=5\,cm\]You need to login to perform this action.
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