To find the image-distance for varying object-distances in case of a convex lens, a student obtains on a screen a sharp image of a bright object placed
very far from the lens. After that he gradually moves the object towards the lens and each time focuses its image of the screen. (a) In which direction – towards or away from the lens, does he move the screen to focus the object? (b) What happens to the size of image – does it increase or decrease? (c) What happen when he moves the object very close to the lens?