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Home Concept Builders Vibrations and Waves Waves - Case Studies Help Help 7

Waves - Case Studies - Questions 7 Help

Frequency, wavelength, and speed are three wave quantities that are related to one another by the formula:

Speed = Frequency • Wavelength

Changing one of the quantities will change at least one other.

There are three similar versions of this question. Here is one of the versions:

Version 1:

The diagram at the right is a snapshot in time of a wave moving along a rope. Which diagram below represents a wave vibrating with the same frequency and moving through a different rope with two times the speed? Tap on an image to select or deselect it.

 
 
 
 
 
 
 

You have to make some decisions to be successful with this question. First you have to decide on how a doubling of speed affects the wavelength. Then you have to decide which diagram displays such a wavelength.

How Does Speed Affect Wavlength?
In this question, the speed at which the wave moves is doubled. If the frequency is not changed, then doubling the speed will affect the wavelength. Speed and wavelength are directly proportional to each other. So the doubling of the speed causes a doubling of the wavelength. You will need to select the wave pattern that shows two times the wavelength (with no change in amplitude).

Deciding on a Diagram
You can use the background grid to determine the wavelength of the wave. You can count the squares. It can be thought of as the distance between one crest and the next adjacent crest. Once you determine the wavelength in the given diagram, it's time to select the answer. The previous section on this Help page describes what type of wavelength you are looking for. You can do the square counting again to determine which pattern displays such a wavelength.

Try these links to The Physics Classroom Tutorial for more help with understanding wave properties:

The Anatomy of a Wave (wavelength and amplitude)

Frequency and Period of Waves

The Speed of a Wave

The Wave Equation

Concept Builder Teacher Notes Directions