A screen is placed at a distance 40 cm away from an illuminated object. A converging lens is placed between the source and the screen and it is attempted to form the image of the source on the screen. If no position could be found, the focal length of the lens

Must be less than 10 cm

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Must be greater than 10 cm

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Must not be greater than 20 cm

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Must not be less than 10 cm

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Solution

The correct option is B
Must be greater than 10 cm

Now, if the image is not being formed on the screen it clearly means the image is being formed beyond the screen or, on the object side of the lens looking at both the cases, we can say that the focal length of the lens must be greater than 10 cm.

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A screen is placed at a distance 40 cm away from an illuminated object. A converging lens is placed between the source and the screen and it is attempted to form the image of the source on the screen. If no position could be found, the focal length of the lens

Q. A screen is placed a distance 40 cm away from an illuminated object. A converging lens is placed between the source and the screen and its is attempted to form the image of the source on the screen. If no position could be found, the focal length of the lens
(a) must be less than 10 cm
(b) must be greater than 20 cm
(c) must not be greater than 20 cm
(d) must not be less than 10 cm.

Q. A light source is placed 100 cm away from a screen. A converging lens placed at a certain position between the source and the screen focuses the image of the source on the screen. The lens is moved a distance of 40 cm and it is found that it again focuses the image of the source on the screen. The focal length of the lens is :

Q. A converging beam of the light forms a sharp image on a screen. A lens is placed in the path of the beam, the lens being

10 c m

from the screen. It is found that the screen has to be moved

8 c m

further away from the lens to obtain a sharp image. Find the focal length and nature of lens.

Q. An illuminated object lies at a distance 1.0 m from a screen. A convex lens is used to form the image of object on a screen placed at distance 75 cm from the lens. Find : (i) the focal length of lens, and (ii) the magnification.

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A screen is placed at a distance 40 cm away from an illuminated object. A converging lens is placed between the source and the screen and it is attempted to form the image of the source on the screen. If no position could be found, the focal length of the lens

The correct option is B Must be greater than 10 cm Now, if the image is not being formed on the screen it clearly means the image is being formed beyond the screen or, on the object side of the lens looking at both the cases, we can say that the focal length of the lens must be greater than 10 cm.

The correct option is B
Must be greater than 10 cm

Now, if the image is not being formed on the screen it clearly means the image is being formed beyond the screen or, on the object side of the lens looking at both the cases, we can say that the focal length of the lens must be greater than 10 cm.