A convex lens has focal length $f$ centimeters. If an object is placed a distance $p$ centimeters from the lens, then the distance $q$ centimeters of the image from the lens is related to $p$ and $f$ by the lens equation
$$\frac{1}{p}+\frac{1}{q}=\frac{1}{f}$$
As shown in the figure on the following page, $p$ must be greater than $f$ for the rays to converge.
(a) Investigate $\lim _{p \rightarrow f^{*}} q$.
(b) What is happening to the image as $p \rightarrow f^{+} ?$