Wavelength in longitudinal waves

Steps:

• Identify compressions (coiled regions) and rarefactions (stretched regions) in the spring diagram.
• Locate two consecutive compressions; the distance between their centers is one wavelength.
• Measure that distance using the diagram's scale or markings.
• Confirm by checking the pattern repeats every that interval across the spring.

Why B is correct:

• B matches the full distance between two consecutive compressions, defining one wavelength per the standard wave property.

Why the others are wrong:

• A: Measures only half-wavelength (compression to rarefaction).
• C: Spans two full wavelengths, overestimating by a factor of 2.
• D: Represents the entire spring length, ignoring the wave's periodic nature.

Final answer: B