Does Frequency Affect Wave Speed

The Speed of a Moving ridge

A wave is a disturbance that moves forth a medium from ane end to the other. If ane watches an sea wave moving along the medium (the ocean water), ane tin detect that the crest of the moving ridge is moving from 1 location to another over a given interval of time. The crest is observed to cover altitude. The speed of an object refers to how fast an object is moving and is usually expressed as the altitude traveled per time of travel. In the case of a moving ridge, the speed is the distance traveled by a given point on the wave (such as a crest) in a given interval of fourth dimension. In equation form,

If the crest of an ocean moving ridge moves a distance of 20 meters in ten seconds, then the speed of the ocean wave is ii.0 m/s. On the other hand, if the crest of an bounding main wave moves a distance of 25 meters in 10 seconds (the aforementioned corporeality of time), then the speed of this sea moving ridge is 2.5 m/s. The faster wave travels a greater distance in the same corporeality of fourth dimension.

Sometimes a moving ridge encounters the cease of a medium and the presence of a different medium. For example, a moving ridge introduced past a person into one end of a slinky will travel through the slinky and eventually reach the terminate of the slinky and the presence of the hand of a second person. I behavior that waves undergo at the end of a medium is reflection. The wave will reflect or bounce off the person'due south hand. When a wave undergoes reflection, information technology remains inside the medium and merely reverses its management of travel. In the case of a slinky wave, the disturbance can exist seen traveling back to the original terminate. A slinky moving ridge that travels to the end of a slinky and back has doubled its distance. That is, by reflecting back to the original location, the wave has traveled a altitude that is equal to twice the length of the slinky.

Reflection phenomena are commonly observed with sound waves. When you let out a holler within a canyon, you ofttimes hear the echo of the holler. The audio moving ridge travels through the medium (air in this example), reflects off the canyon wall and returns to its origin (you). The result is that you hear the repeat (the reflected audio wave) of your holler. A classic physics trouble goes like this:

Noah stands 170 meters away from a steep canyon wall. He shouts and hears the echo of his voice one 2nd afterwards. What is the speed of the wave?

In this instance, the audio wave travels 340 meters in i 2d, so the speed of the moving ridge is 340 m/s. Recall, when there is a reflection, the wave doubles its distance. In other words, the distance traveled by the sound wave in 1 second is equivalent to the 170 meters down to the coulee wall plus the 170 meters back from the coulee wall.

Variables Affecting Moving ridge Speed

What variables bear upon the speed at which a wave travels through a medium? Does the frequency or wavelength of the wave affect its speed? Does the amplitude of the wave affect its speed? Or are other variables such every bit the mass density of the medium or the elasticity of the medium responsible for affecting the speed of the moving ridge? These questions are often investigated in the course of a lab in a physics classroom.

Suppose a wave generator is used to produce several waves inside a rope of a measurable tension. The wavelength, frequency and speed are determined. So the frequency of vibration of the generator is changed to investigate the outcome of frequency upon wave speed. Finally, the tension of the rope is altered to investigate the issue of tension upon wave speed. Sample information for the experiment are shown below.

Speed of a Moving ridge Lab - Sample Data

Trial	Tension (N)	Frequency (Hz)	Wavelength (thou)	Speed (m/s)
1	2.0	iv.05	4.00	16.ii
2	2.0	eight.03	ii.00	16.1
three	2.0	12.thirty	ane.33	16.4
4	2.0	16.2	ane.00	16.two
5	2.0	20.2	0.800	16.2
6	5.0	12.8	2.00	25.six
7	5.0	19.three	1.33	25.7
8	v.0	25.5	1.00	25.5

In the beginning five trials, the tension of the rope was held constant and the frequency was systematically changed. The information in rows 1-5 of the tabular array above demonstrate that a change in the frequency of a wave does not affect the speed of the wave. The speed remained a well-nigh abiding value of approximately 16.ii m/s. The pocket-size variations in the values for the speed were the result of experimental error, rather than a demonstration of some physical law. The data convincingly show that wave frequency does not affect moving ridge speed. An increase in wave frequency caused a decrease in wavelength while the wave speed remained abiding.

The last three trials involved the same procedure with a different rope tension. Discover that the speed of the waves in rows half dozen-8 is distinctly different than the speed of the moving ridge in rows i-v. The obvious cause of this difference is the alteration of the tension of the rope. The speed of the waves was significantly higher at higher tensions. Waves travel through tighter ropes at higher speeds. So while the frequency did non bear on the speed of the moving ridge, the tension in the medium (the rope) did. In fact, the speed of a wave is not dependent upon (causally affected by) backdrop of the wave itself. Rather, the speed of the wave is dependent upon the backdrop of the medium such as the tension of the rope.

1 theme of this unit has been that "a wave is a disturbance moving through a medium." There are 2 distinct objects in this phrase - the "wave" and the "medium." The medium could be water, air, or a slinky. These media are distinguished past their properties - the textile they are made of and the concrete properties of that material such as the density, the temperature, the elasticity, etc. Such physical properties describe the material itself, not the wave. On the other hand, waves are distinguished from each other by their backdrop - amplitude, wavelength, frequency, etc. These backdrop depict the wave, not the material through which the wave is moving. The lesson of the lab activeness described to a higher place is that wave speed depends upon the medium through which the wave is moving. Only an amending in the properties of the medium will cause a change in the speed.

We Would Like to Suggest ...

Why just read about it and when yous could be interacting with it? Interact - that's exactly what you do when you utilise 1 of The Physics Classroom's Interactives. We would like to suggest that yous combine the reading of this page with the apply of our Slinky Lab Interactive. You lot can observe information technology in the Physics Interactives section of our website. The Slinky Lab provides the learner with a unproblematic environment for exploring the movement of a wave along a medium and the factors that bear upon its speed.

Check Your Understanding

1. A instructor attaches a slinky to the wall and begins introducing pulses with different amplitudes. Which of the 2 pulses (A or B) beneath volition travel from the hand to the wall in the least amount of time? Justify your answer.

2. The teacher then begins introducing pulses with a different wavelength. Which of the two pulses (C or D) volition travel from the mitt to the wall in the to the lowest degree corporeality of time ? Justify your answer.

iii. The time required for the sound waves (v = 340 m/s) to travel from the tuning fork to point A is ____ .

a. 0.020 2d

b. 0.059 second

c. 0.59 second

d. 2.9 second

4. 2 waves are traveling through the aforementioned container of nitrogen gas. Moving ridge A has a wavelength of 1.5 m. Wave B has a wavelength of four.five m. The speed of wave B must be ________ the speed of wave A.

a. one-ninth

b. i-third

c. the same as

d. three times larger than

5. An automatic focus camera is able to focus on objects past use of an ultrasonic audio wave. The camera sends out sound waves that reflect off distant objects and return to the camera. A sensor detects the fourth dimension it takes for the waves to return and then determines the distance an object is from the camera. The photographic camera lens then focuses at that distance. Now that's a smart camera! In a subsequent life, you might have to be a camera; so try this problem for do:

If a sound moving ridge (speed = 340 1000/south) returns to the camera 0.150 seconds afterward leaving the camera, and then how far abroad is the object?

half-dozen. True or FALSE:

Doubling the frequency of a wave source doubles the speed of the waves.

7. While hiking through a canyon, Noah Formula lets out a scream. An echo (reflection of the scream off a nearby coulee wall) is heard 0.82 seconds after the scream. The speed of the sound moving ridge in air is 342 m/s. Calculate the distance from Noah to the nearby canyon wall.

8. Mac and Tosh are resting on pinnacle of the water near the end of the pool when Mac creates a surface moving ridge. The moving ridge travels the length of the pool and back in 25 seconds. The pool is 25 meters long. Determine the speed of the wave.

9. The water waves beneath are traveling forth the surface of the ocean at a speed of 2.five m/due south and splashing periodically against Wilbert's perch. Each adjacent crest is five meters autonomously. The crests splash Wilbert'due south feet upon reaching his perch. How much time passes between each successive drenching? Answer and explicate using complete sentences.