Question

The image of an object formed by a lens of the screen is not in sharp focus. Suggest a method to get clear focussing of the image on the screen without disturbing the position of the object, the lens or the screen?

Answer 1

We can use another lens (converging or diverging) depending upon the focus of the fixed lens. We can adjust the position of this new lens to obtain a sharp image on the screen. And this is done without disturbing the position of the object, the lens (original one) or the screen. The concept behind this is: addition of lens in the system changes the effective focal length of the lens system.