tbr physics section 5 passage 2 (Speed of a wave Q)

[beeltix]

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This is the question:

How does the speed ofthe wave on String I compare to
the speed of the wave on String II?
A. Wave I is twice as fast as Wave II.
B. Wave II is twice asfast as Wave I.
C. The wave speeds of the two waves are equal.
D. There is no way to determine the relative wave
speeds

I assumed C because I ALWAYS thought the V is not affected by f or wavelength but only the medium but the answer is...

"Choice B is the best answer. Both waves are generated using an external oscillator set at 60 Hz, so they each have the same
frequency, 60 Hz. Both waves must obey v = Xf. However, from the picture, we see that Wave I has only half the
wavelength of Wave II. Hence, Wave I can have only half the speed of Wave II. The best answer is choice B"

So.... what? can someone clarify this? So V IS affected by f and wavelength? Is there an exception?

 

[Lunasly]

If I remember correctly, I also got this question wrong. All waves must follow v = (lambda)(frequency). I believe that all forms of electromagnetic radiation travel at the same speed in any given medium. Therefore, to maintain the same speed, you have to alter the wavelength and the frequency of the wave. If the wavelength of the wave decreases, then its frequency must increase to maintain the same speed. In this question, two waves have the exact same frequency. Therefore, in order to travel at the same speed, they have to have same wavelength (according to v = (lambda)(frequency)). However, when comparing the two diagrams, we see that wave I has only half the wavelength of wave II. The only reasonable conclusion we can make from this is that the speed at which each wave propagates are different.

 

[beeltix]

Ohhhhh Thanks for clearing that up for me!