2. Consider an imaging system using a lens with focal length 4cm having an image plane 6cm behind the lens. Assume the lens diameter is 1cm. a) How far in front of the lens on the optical axis of the system must we place a point to get an image without blur? b) Suppose the image plane has an active area of 2cm2cm which is partitioned into 1000 1000 square pixels. Supose the point in part a) images without blur to the center of a pixel. How far can we move the point in focus towards the lens before the image of the point extends to more than one pixel