Joby draws a bow across a cello string and looks closely. The string blurs into humps, and the humps stay exactly where they are.
Every wave so far traveled: crests moved along ropes, ripples crossed tanks. These humps refuse to travel. This lesson tells the two kinds apart.
The cello humps look nothing like a pond ripple. A fair comparison needs both behaviors on one rope.
Kerstin shakes a long rope at an easy, steady rhythm. Crests travel along the rope, passing one point after another: the pattern moves along the medium.
A wave whose pattern moves along the medium is called a traveling wave.
Kerstin keeps the same rope and finds just the right shaking rhythm. Now no hump moves along the rope: each hump swings up and down in place.
A wave whose pattern stays in place while the medium oscillates is called a standing wave.
The cello string's humps stay put, so the bowed string holds a standing wave. A pond ripple's crests move on, so the ripple is a traveling wave.
A flag rope on a windy day shows three humps that swing widely but never move along the rope. Is this a standing wave or a traveling wave?
The pattern stays in place while the rope oscillates.
A standing wave.
A single pulse from a flicked garden hose runs from the hand to the far end. Is this a standing wave or a traveling wave?
The pattern moves along the medium, passing one point after another.
A traveling wave.
Ripples from a dropped pebble spread across a puddle, each crest moving outward. Is this a standing wave or a traveling wave?
A plucked banjo string blurs into humps that swing in place between the fixed ends. Is this a standing wave or a traveling wave?
Ilka says: 'On a standing wave, the medium still oscillates even though the pattern stays in place.' Is Ilka correct?
Which of these is a standing wave?
What tells you a wave on a cord is a standing wave rather than a traveling wave?
A long bungee cord is tied between two trees. Joby shakes one end steadily, and five humps appear along the cord, each swinging up and down without moving toward either tree. Which kind of wave is on the cord?