Question

For a certain transverse wave, the distance between two successive crests is 1.20 m and eight additional crests pass a given point along the direction of travel every 13.00 s. calculate the wave speed.

Answer 1

The distance between two succesive crests of a wave corresponds to its wavelength, therefore the wavelength of this wave is
$\lambda=1.20 m$

The frequency of a wave is the number of crests that passes through a given point in a certain time; therefore, for this wave it is:
$f= \frac{N}{t}= \frac{8}{13.00 s}=0.62 Hz$

And now we can calculate the wave speed, which is given by the product between the wavelength and the frequency:
$v= \lambda f = (1.20 m)(0.62 Hz)=0.74 m/s$