Question

A student used a device (X) to obtain/focus the image of a well illuminated distant building on a screen (S) as shown below in the diagram. Select the correct statement about the device (X).

Answer 1

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Since the object was obtained on the screen, so the image formed was real. So, the lens is convex lens. Moreover, as given in the diagram, the distance between the object and the screen is 8 cm i.e. focal length =8cm
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Answer 2

Answer: (D) The device is a convex lens at a focus length of 8 cm.

Explanation:

Convex lens is also known as converging lens when double convex lens are used. It focuses all the diverging, blurred light rays and all parallel light rays pass through it and then bends inward to converge at a focal point.

Thus using a double convex lens the light rays of an illuminated distant building image was obtained on the screen.