$3$ A single point of light can be modeled by a digital image consisting of all $0\text{'}$s$,$ with a $1$ in the location of the point of light. If you view a single point of light through a defocused lens, it will appear as a fuzzy blob whose size depends on the amount by which the lens is defocused. We mentioned in Section $3\mathrm{.}5$ that filtering an image with a box kemel is a poor model for a defocused lens, and that a better approximation is obtained with a Gaussian kernel. Using the single$-$point$-$of$-$light analogy, explain why this is so$.$