A converging lens lies in between the luminous toy and the screen.The screen is moved a few centimetres away from a luminous toy,how would you adjust the position of the lens so that a sharp image can once again be formed on the screen?
The converging lens lies in between the luminous toy and the screen. An assumption has been made that a sharp image of the toy is formed on the screen in this case. The screen is now moved a few centimeters away from a luminous toy. This also moves the screen away from the converging lens by an equal distance.
To form a sharp image on the screen again, the converging lens would have to be moved towards the screen such that the distance from the lens to the screen is equal to the focal length of the lens. Once this is achieved a sharp image of the toy is formed on the screen once again.