A) 12
B) 11
C) 10
D) 13
Correct Answer: A
Solution :
For objective lens \[\frac{1}{{{f}_{o}}}=\frac{1}{{{v}_{o}}}-\frac{1}{{{u}_{o}}}\] Þ \[\frac{1}{{{v}_{o}}}=\frac{1}{{{f}_{o}}}+\frac{1}{{{u}_{o}}}\]\[=\frac{1}{4}+\frac{1}{-5}=\frac{1}{20}\]Þ \[{{v}_{o}}=20cm\] Now \[M=\frac{{{v}_{o}}}{{{u}_{o}}}\left( 1+\frac{D}{{{f}_{e}}} \right)\] \[=\frac{20}{5}\left( 1+\frac{20}{10} \right)\] \[=12\,.\]
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