Q170 / 200 · Manipal (MET) 2010 · Physics

A convex lens is placed between object and a screen. The size of object is 3 cm and an image of height 9 cm is obtained on the screen. When the lens is displaced to a new position, what will be the size of image on the screen?

A
2 cm
B
6 cm
C
4 cm
Correct answer
D
1 cm

Solution

From displacement method size of object, $O=\sqrt{I_1 I_2}$ Here, $O=3 \mathrm{~cm}, I_1=9 \mathrm{~cm}$, $\begin{array}{ll}\therefore & 3=\sqrt{9 I_2}\end{array}$ or $I_2=1 \mathrm{~cm}$

Hence, the correct answer is option: 'D'.

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