When you tune in a radio station using an old-fashioned rotating dial you don't
have to be exactly tuned in to the right frequency in order to get the station. If you did, the tuning would be infinitely sensitive, and you'd never be able to receive any signal at all!
Instead, the tuning has a certain amount of "slop" intentionally designed into it. The strength of the received signal can be expressed in terms of the dial's setting by a function of the form where , , and are constants. This functional form is in fact very general, and is
encountered in many other physical contexts. The graph below shows the resulting bell-shaped curve. Find the frequency at which the maximum response occurs, and show that
if is small, the maximum occurs close to, but not exactly
at, .