Figure 1: (a), (c), and (e) are the luminance figures of an LED measured by a Lutron LX-102 light meter. Their corresponding frequency representations are given in (b), (d), and (f), respectively. The spectrum of the square wave strictly adheres to theory, that is, a peak demonstrated at fundamental frequency as well as a peak at the harmonic. The sine wave and the triangle wave do not. They have weak harmonics that should not exist at . However, these harmonics should not affect the result, since their strength are one tenth that of the fundamental frequency.