Wavelength is typically measured as the distance between two consecutive points in phase on a wave. The most common ways to measure wavelength include:
- From the crest of one wave to the crest of the next wave.
- From the trough of one wave to the trough of the next wave.
- From one point on the wave to the corresponding point on the next wave (e.g., from the midpoint of one crest to the midpoint of the next crest).
The options provided in your question can be clarified as follows:
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From the still water level to the crest: This measurement is not considered wavelength; it measures the wave height (amplitude).
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From the still water to the trough: This is also a measurement of wave height or amplitude, not wavelength.
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From the crest of one wave to the crest of the next: This is the correct measurement for wavelength.
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From trough to crest: This does not represent wavelength but measures the height from the lowest point (trough) to the highest point (crest) of a wave.
In summary, the correct way to measure wavelength is "from the crest of one wave to the crest of the next" or equivalently "from trough to trough."