Home » Alternating Current » 5 » d An impure signal is found to have 2 kHz and 4 kHz components. This 4 kHz signal is:   a.   a fundamental of the 2 kHz signal   b.   a sub-harmonic of 2 kHz   c.   the DC component of the main signal   d.   a harmonic of the 2 kHz signal Your answer "d" is CORRECT! It is actually the second harmonic, because it is two times the other frequency. Next