Physics
Signal Frequency Components
Quick fact
A square wave—often used in digital electronics—is actually made up of an infinite series of odd-numbered sine wave harmonics (e.g., 1st, 3rd, 5th frequencies).
Why this is interesting
You hear a single note from a piano, but did you know that note is actually a blend of many pure tones? How does your ear tell one instrument from another if they play the same pitch?