Question

When an object is placed 30 cm away from a converging lens of focal length 20 cm the image formed is positioned 60 cm from the lens. If the object is moved 5 cm closer to the lens, the position of the image will change as :
(a) it will come closer to lens and will became erect.
(b) it will go away form lens and will remain inverted .
(c) it will come closer to lens and will remain inverted.
(d) it will go away from lens and will become erect.

Answer 1

$$\begin{gathered} U\sin gLenseFormulae\frac{1}{f}=\frac{1}{v}-\frac{1}{u} \\ ObjectDis\tan ce,u=-25(forconvexlense) \\ ImageDis\tan ce,v=? \\ FocalLength,f=20cm \\ \frac{1}{20}=\frac{1}{v}-\frac{1}{-25} \\ \Rightarrow v=100cm \\ magnification,m=\frac{100}{-25}=-4 \\ Sotheimagewillformawayatrightsideandremaininverted. \end{gathered}$$