transverse

Meaning: In a transverse wave the displacement is perpendicular to the direction of energy transport. On a string, each piece moves up and down while the pulse travels along the string. Wavelength is the distance from crest to crest. In light, the electric and magnetic fields oscillate perpendicular to each other and to the direction of travel, so no medium is needed. Mechanical transverse waves need a medium that resists shear, such as a string or a solid. Sound in a fluid is longitudinal.

Equation: v = fλ, where v is wave speed (m/s), f is frequency (Hz), and λ is wavelength (m). For a string, v = √(FT/μ), where FT is tension (N) and μ is mass per unit length (kg/m).

On the MCAT: Expect classification questions: light, string waves and seismic S waves are transverse; sound and seismic P waves are longitudinal. Polarization questions use the fact that a filter blocks or passes transverse waves depending on orientation. String problems ask how tension or density changes speed; frequency is set by the source, so λ changes when v changes.

Common confusion: Transverse does not mean the medium travels along with the wave, or that motion must be vertical. The medium oscillates about equilibrium, and the direction of that motion is perpendicular to propagation. The test is perpendicular versus parallel.