Harmonics problem. A square wave of frequency f contains harmonics (sine waves) at f, 3f, 5f, 7f, ... .Suppose a system responds to frequencies in the range 20-40 kHz but is insensitive outside of this range. EXAMPLE: Imagine applying a square wave with f = 30 kHz to this system. What is the shape of the response? [ a 30 kHz sine wave. ] QUESTION: Imagine applying a square wave with f = 10 kHz to this system. What is the shape of the response?