A) 8.6 cm
B) 6.2 cm
C) 10 cm
D) 4.4 cm
Correct Answer: D
Solution :
Concave lens forms the virtual image of a real object. So let \[u=-4x\]and \[v=-x\]then \[3x=10\,cm\]or \[x=\frac{10}{3}\,cm\] \[\therefore \]\[u=\frac{-40}{3}cm\]and \[v=-\frac{10}{3}\,cm\] Substituting in \[\frac{1}{f}=\frac{1}{v}-\frac{1}{u},\]we get \[\frac{1}{f}=-\frac{3}{10}+\frac{3}{40}\]or \[f=-\frac{40}{9}=-4.4\,cm.\] Hence, the correction option is [d].You need to login to perform this action.
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