A) 7.2 m
B) 2.4 m
C) 3.2 m
D) 5.6 m
Correct Answer: D
Solution :
\[\frac{1}{f}=\frac{1}{12}+\frac{1}{240}=\frac{20+1}{240}\] \[f=\frac{240}{21}m\] shift \[=1(1-\frac{2}{3})=\frac{1}{3}\] Now v? \[=12-\frac{1}{3}=\frac{35}{3}\,\,cm\] \[\therefore \frac{21}{240}=\frac{3}{35}-\frac{1}{u}\] \[\frac{1}{u}=\frac{3}{35}-\frac{21}{240}=\frac{1}{5}\left( \frac{3}{7}-\frac{21}{48} \right)\] \[\frac{5}{u}=\left| \frac{144-147}{48\times 7} \right|\] \[u=560\,\,cm=5.6\,m\]You need to login to perform this action.
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