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

2 c m

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6 c m

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4 c m

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1 c m

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Solution

The correct option is D $1 c m$
The given problem is an example of displacement method, which is generally used to measure the focal length of the lens. In this method, the two image sizes and the object size are related as:
$O = \sqrt{I_{1} I_{2}}$
$⟹ 3 = \sqrt{9 \times I_{2}}$
$I_{2} = 1 c m$

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

The correct option is D 1cmThe given problem is an example of displacement method, which is generally used to measure the focal length of the lens. In this method, the two image sizes and the object size are related as:O=√I1I2⟹3=√9×I2I2=1 cm

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

The correct option is D $1 c m$
The given problem is an example of displacement method, which is generally used to measure the focal length of the lens. In this method, the two image sizes and the object size are related as:
$O = \sqrt{I_{1} I_{2}}$
$⟹ 3 = \sqrt{9 \times I_{2}}$
$I_{2} = 1 c m$