Sound waves: type and frequency calculation

Steps:

• Identify wave type: sound waves are longitudinal, involving particle compression/rarefaction.
• Examine graph: assumes time axis for periodic oscillations, typical for sound representation.
• Measure period: distance between peaks gives one cycle time, e.g., 20 ms.
• Calculate frequency: f = 1/T = 1/0.02 s = 50 Hz.

Why B is correct:

• Sound waves are longitudinal by definition (parallel particle displacement to propagation); frequency f = 1/T, where T = 20 ms yields 50 Hz.

Why the others are wrong:

• A: Period is 20 ms (not 25 ms), giving 50 Hz, not 40 Hz.
• C: Sound waves are longitudinal (not transverse); amplitude likely in pressure units, not 5 μm displacement.
• D: Sound waves are longitudinal (not transverse); wavelength measures spatial distance, not time in ms.

Final answer: B