A student determines the focal length of a device X, by focussing the image of a far off object on the screen positioned as shown in the figure alongside.

The device X is a :
(1) Convex lens
(2) Concave lens
(3) Convex mirror
(4) Concave mirror

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Solution

As all the rays are reflected and converged after falling on the device X, and the image is focussed on the screen, the device X is a converging mirror or concave mirror which forms an image of a far off object by converging the rays on its focus.

Hence, the correct answer is option 4.

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A student determines the focal length of a device X, by focussing the image of a far off object on the screen positioned as shown in the figure alongside. The device X is a : (1) Convex lens (2) Concave lens (3) Convex mirror (4) Concave mirror

As all the rays are reflected and converged after falling on the device X, and the image is focussed on the screen, the device X is a converging mirror or concave mirror which forms an image of a far off object by converging the rays on its focus. Hence, the correct answer is option 4.

A student determines the focal length of a device X, by focussing the image of a far off object on the screen positioned as shown in the figure alongside.

The device X is a :
(1) Convex lens
(2) Concave lens
(3) Convex mirror
(4) Concave mirror

As all the rays are reflected and converged after falling on the device X, and the image is focussed on the screen, the device X is a converging mirror or concave mirror which forms an image of a far off object by converging the rays on its focus.

Hence, the correct answer is option 4.