The simple equation v = λf shows how the wave speed, wavelength, and
frequency are interconnected. It’s the most basic equation in wave
theory—know it for the test.
- A traveling wave on a rope has a frequency of 2.5 Hz. If the
speed of the wave is 1.5 m/s, what are its period and wavelength?
Here’s How to Crack It
The period is the reciprocal of the frequency.
The wavelength can be found from the equation λf = v.
- The period of a traveling wave is 0.5 s, its amplitude is 10 cm,
and its wavelength is 0.4 m. What are its frequency and wave
speed?
Here’s How to Crack It
The frequency is the reciprocal of the period: f = 1/T = 1/(0.5 s) = 2 Hz. The wave
speed can be found from the equation v = λf.
v = λf = (0.4 m)(2 Hz) = 0.8 m/s
(Notice that the frequency, period, wavelength, and wave speed have nothing to do
with the amplitude.)