A) 10 cm
B) 20 cm
C) 30 cm
D) 40 cm
Correct Answer: B
Solution :
When magnification is \[+2,u=x,v=-2x,f=20\]Using \[\frac{1}{v}+\frac{1}{u}=\frac{1}{f},-\frac{1}{2x}+\frac{1}{x}=\frac{1}{20}\]or \[x=10\,cm\]To have a magnification of \[-2,u=y,v=2y,f=20\] \[\therefore \]\[\frac{1}{2y}+\frac{1}{y}=\frac{1}{20}\]or \[y=30\,cm\] \[\therefore \]\[y-x=20\,cm.\] Hence, the correction option is [b].You need to login to perform this action.
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