wave
Summary
A wave is a disturbance that carries energy from place to place without net transport of the medium itself. Mechanical waves need a medium; electromagnetic waves do not. Most testable: v = fλ, and at a boundary the frequency stays fixed while speed and wavelength change.
Detail
Meaning: A wave is a disturbance that transfers energy from one place to another while the particles of the medium oscillate about their equilibrium positions. Mechanical waves, such as sound and waves on a string, need a medium. Electromagnetic waves do not, and travel at c = 3.00 × 10⁸ m/s in vacuum. In a transverse wave the oscillation is perpendicular to the direction of travel; in a longitudinal wave, such as sound, it is parallel.
Equation: v = fλ, where v is wave speed (m/s), f is frequency (Hz = s⁻¹), and λ is wavelength (m). Period is T = 1/f, with T in seconds.
On the MCAT: Passages show displacement versus position (read λ) or versus time (read T), then ask for speed. When a wave enters a new medium, the source fixes f, so frequency stays the same while speed and wavelength change together. Intensity rises with amplitude squared.
Common confusion: Students picture the medium traveling with the wave, or think speed rises with frequency. Speed is set by the medium (for a string, tension and linear density), so raising f shortens λ and leaves v unchanged.
Sources
- Physics (Cutnell and Johnson)
- Physics (Giancoli)
- Fundamentals of Physics (Halliday, Resnick, and Walker)
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.