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Wave Basics - help9

The wavelength of a wave is the length of the repeating unit within the wave pattern. Knowledge of the length of the pattern and the number of waves (repeating units) present in the pattern allows one to determine the wavelength.

There are three similar versions of this question. Here is one of those versions:

Version 1:
The diagram represents a snapshot in time of a wave traveling through a Slinky. Use the background grid to determine the wavelength of the wave. Each square measures 1-cm along its edge.

The diagram shows a longitudinal wave pattern. If you inspect any wave pattern, you will notice that there is a repeating unit that occurs over and over again along the length of the pattern. This repeating unit is known as a wave. The repeating unit includes a region with a compression and a second region with a rarefaction. The length of this repeating unit is known as the wavelength. You can use the background grid to measure it.

Wavelength is often thought of as the distance from a crest to the next adjacent crest. But that definition does not work for longitudinal waves like this one. So for a longitudinal wave, the wavelength is measured from the center of a compression to the center of the next adjacent compressoin. This can be easily measured on the diagram.

Try this link to The Physics Classroom Tutorial for more help with the concept of wavelength:

The Anatomy of a Wave