The wavelength of a wave is the length of the repeating unit within the wave pattern. Knowledge of the length of the pattern and the number of waves (repeating units) present in the pattern allows one to determine the wavelength.
Getting your Trinity Audio player ready...
Hold down the T key for 3 seconds to activate the audio accessibility mode, at which point you can click the K key to pause and resume audio. Useful for the Check Your Understanding and See Answers.
Wavelength - help11
There are three similar versions of this question. Here is one of those versions:
Version 1:
A rope is vibrating at high frequency. The length of the rope is 4.00 meters. A snapshot of the rope at a given moment in time is also shown. Use this information to determine the wavelength of the wave.
In this question, the length of a rope is given. The wave pattern established in the rope is shown. You must determine the wavelength from these two pieces of data. To do so, you will need to relate the number of waves shown in the pattern to the length.Perhaps the easiest way to determine the number of waves is to know what a half-wave looks like. The diagram at the right displays one-half of a wave. One complete wave consists of two halves - the half with the crest and the half with the trough. So simply count the number of halves and divide the result by two in order to determine the number of waves in the pattern.
Once done, you can write an equation of the form N•W = L where N is the number of waves (determined from previous paragraph), W is the wavelength (what you are trying to calculate), and L is the given length. Use the equation to solve for W. You will have to divide L by N to determine the wavelength.
Try this link to The Physics Classroom Tutorial for more help with the concept of wavelength:
The Anatomy of a Wave