I am a physics teacher and I was discussing interference patterns related to tuning forks with a colleague. She demonstrated the interference, which was very obvious. As she rotated the tuning fork, the volume of the tone increased and decreased dramatically. She showed me this diagram as a reference when explaining the phenomenon.
This explanation does not make sense to me for two reasons: 1) Assuming that the diagram referenced is correct, I do not understand how any point in space could be a half-wavelength further from one tine than the other when the tines are only 0.02m apart and the wavelength produced is approximately 1.3m. 2) The diagram referenced shows areas of compression leaving each tine simultaneously and traveling outwards in concentric circles. That does not seem likely to me. If the tines are vibrating back and forth, it seems that whenever an area of compression left one side of the tine, an area of rarefaction should leave the other side of the tine.
Am I thinking about this incorrectly? Any explanations?