Are standing waves in guitars longitudinal or transverse?
The standing wave is in the guitar string, trapped between the string connections and/or the frets your fingers push down on. That wave is transverse and you can picture why. The string itself is moving up and down but standing waves keep getting reflected back and forth between the “walls” (string connections, frets). If the string was disconnected and you sent a wave through it, like in the case of a whip, the up and down motion would go across the string but the string itself wouldn’t move. The motion of the medium the wave travels through (the string) and the direction the wave actually moves would be at right angles, or transverse, hence the name transverse wave. However, the guitar string vibrating is displacing air molecules. These molecules bang into each other causing waves of their own. It’s like the effect of coils hitting each other in a spring. There’s a packet of closely spaced coils that travels through the spring. If you’ve ever seen a slinky or some physics lab demonst
