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Standing and Progressive

Waves can also be categorized as either standing or progressive. Progressive waves transfer energy from A to Bae to bee, and so their peaks appear to move. For standing waves, they do not. In the real world, most waves occur as progressive waves - ocean waves and sound waves for example.

Standing waves occur as a special case when waves are confined in space. For progressive waves all points along the wave oscillate the same amount, this is not the case for standing waves where the amount of oscillation depends on the position. They contain special points called nodes that do not move at all and anti-nodes that oscillate the most. Standing waves are hard to find naturally as they only occur under certain circumstances, but musicians make use of them all the time. The strings on a guitar oscillate in a standing wave when they are plucked for example.

Depicted is the difference between standing and progressive waves. The displacement-position graphs are shown for two waves, one above the other. The plots are both drawn with a blue line and have a sine curve shape. The first is a standing wave which exists between two fixed points, shown with dark-blue dots. This wave does not propagate, meaning the position of the peaks and troughs will not change over time. The oscillation of individual particles is depicted using red arrows, with the amount of oscillation varying with position. An Antinode, where particles oscillate maximally, is labelled with a pink dot. These correspond to the peaks and troughs of the wave. A node, where there is no particle oscillation, is labelled with a green dot. The second wave is a progressive wave which propagates to the right, meaning the position of the peaks and troughs will change over time. The oscillation of individual particles is depicted using red arrows, with the amount of oscillation being the same for all positions.

Figure 1: Diagram showing the difference between standing and progressive waves.