Since the direction in which the rope oscillates (vertically) is perpendicular to the
direction in which the wave propagates (or travels, horizontally), this wave is
transverse. The time it takes for one complete vertical oscillation of a point on the
rope is called the period, T, of the wave, and the number of cycles it completes in
one second is called its frequency, f. The period and frequency are established by
the source of the wave and T = 1/f.
Four of the most important characteristics of any wave are its wavelength,
amplitude, period, and frequency.
A fifth important characteristic of a traveling wave is its speed, v. Look at the
figure above and imagine the visible point on the rope moving from its crest
position, down to its trough position, and then back up to the crest position. How
long did this take? The period, T. Behind the screen, the wave moved a distance of
one wavelength. T is the time required for one wave to travel by a point, and λ is
the distance traveled by one wave. Therefore, the equation distance = rate × time
becomes