wave speed
Summary
Wave speed is how fast a wave pattern, such as a crest, advances through a medium: v = fλ. At MCAT level the medium sets it, not the source. When a wave enters a new medium, frequency stays constant while speed and wavelength change in proportion.
Detail
Meaning: Wave speed is how fast the wave pattern, such as a crest, advances through a medium. It is not the speed of the medium's particles, which oscillate in place. The source sets the frequency, the medium sets the speed, and the wavelength follows from the two.
Equation: v = fλ, where v is wave speed (m/s), f is frequency (Hz), and λ is wavelength (m). For a stretched string, v = √(T/μ), where T is tension (N) and μ is mass per unit length (kg/m). For light in a medium, v = c/n, where c = 3.00 × 10⁸ m/s and n is the unitless index of refraction.
On the MCAT: A wave enters a new medium: frequency stays constant, so speed and wavelength change in proportion. A higher n slows light and shortens λ. Greater string tension raises speed. Sound is generally faster in solids than in liquids, and faster in liquids than in gases.
Common confusion: Raising the frequency does not speed up a wave in the same medium; the wavelength shrinks instead. Wave speed is also different from the velocity of the vibrating particles.
Sources
- College Physics
- Fundamentals of Physics
- Physics
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.