Question on waves

[abadri421]

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In EK it states that the velocity of a wave is the product of wavelength and frequency. And that the velocity is dictated by the medium through wich the wave travels..Now that i understand but does this apply to waves created by a string in the case of a machine increasing and decreasing the frequency to create different wavelengths??

 

[inside_edition]

In EK it states that the velocity of a wave is the product of wavelength and frequency. And that the velocity is dictated by the medium through wich the wave travels..Now that i understand but does this apply to waves created by a string in the case of a machine increasing and decreasing the frequency to create different wavelengths??

v=wavelength*frequency ---this is always true

when a wave goes through a medium (light through glass, sound through water, for example) frequency does not change but wavelength/velocity can change.

 

[abadri421]

But what about waves on a string? will changing the frequency, gven the wavelength, change the velocity?

 

[RPedigo]

But what about waves on a string? will changing the frequency, gven the wavelength, change the velocity?

As the machine increases the frequency, you'll see the waves getting shorter. This is because they have to be inversely proportional to keep velocity constant. Recall that for waves on a string, the velocity is equal to the square root of the tension divided by the linear density. Notice that frequency is nowhere to be found in this equation.

Edit: Actually, I could be wrong, if changing the frequency changes the tension... I'm really not terribly sure; hopefully someone can confirm or correct my post.

 

[swifteagle43]

Energy = h * v

v = c * lambda

lambda * frequency = V

where lambda = wavelength

 

[emquiksilver]

The speed of a wave depends on the medium. Same medium, same speed. Changing frequency will change wavelength. Also, different medium, different speed. So frequency stays the same when you change medium.

 

[RPedigo]

v = c * lambda

No.

 

[ArchieMoses]

Now that i understand but does this apply to waves created by a string in the case of a machine increasing and decreasing the frequency to create different wavelengths??

Hrm, yeah i'm pretty sure that's right as long as the wave that the machine is altering stays in the same medium. The machine may alter the frequency and thus change the wavelength (velocity stays the same), or vice versa.

 

[swifteagle43]

No.

i meant

c/v = n

 

[Blondnuttyboy]

or - E = hv/lambda

E = hf

once again, freq stands independent of the v and lambda relationship

 

[Richter915]

As the machine increases the frequency, you'll see the waves getting shorter. This is because they have to be inversely proportional to keep velocity constant. Recall that for waves on a string, the velocity is equal to the square root of the tension divided by the linear density. Notice that frequency is nowhere to be found in this equation.



Edit: Actually, I could be wrong, if changing the frequency changes the tension... I'm really not terribly sure; hopefully someone can confirm or correct my post.

A change in frequency does result in a change in tension because of the equation f = v/2L where v, like you said, is the square root of the tension divided by linear density. The relationship between f and T is a result of f relating to T. When you change T and keep wavelength the same, f will go up and v will go up when T goes up. This is why when you increase the tension on a guitar string, you get a higher pitch because there's a higher frequency. Like you said, the higher frequency will result in a shorter wavelength thus leaving v constant in the end...hope this makes sense.