Question

An illustration of a ringing bell and dots representing air molecules. The dots are close together, then far apart and close together again representing a longitudinal mechanical wave of sound going from the bell to an ear.
How many wavelengths are seen in this image of a sound wave?

three
four
six
ten

Answer 1

I can’t see the picture — could you upload it or describe how many regions of “dots close together” (compressions) and “dots far apart” (rarefactions) are shown?

How to count: one wavelength is the distance from one compression to the next compression (or from one rarefaction to the next). So the number of complete wavelengths equals the number of compressions (or rarefactions) minus 1. For example, if the picture shows 4 compressions, there are 3 wavelengths (answer: three).