More on Waves: 4 Items

1) As noted earlier several of you have decided that wavespeed increases if frequency does. Once again, this is not true and the equation lambda f = v is very misleading and should be written as lambda = cT or lambda = c/f. This properly indicates that the two independent quantities c and f both affect lambda. Wavespeed is given by sqrt(FT/(M/L)) for transverse waves and sqrt(Y/density) for longitudinal waves. See notes on these.

2)There is a velocity affected by the frequency but pay close attention to the following: By now you should have noticed that I never use v for the wavespeed, I use c. The wavespeed is not the velocity of a physical particle. No matter is moving at speed c. Matter moves at a velocity which is determined by the frequency and the amplitude because the matter is oscillating. For example, in a horizontally traveling transverse wave, where y = A sin ( omega t - kx), the matter is going up and down, with a velocity = omega A cos (omega t -kx). This physical velocity IS NOT the wavespeed. Omega here is 2pi f as usual and is also 2pi c/lambda. Once again, the frequency, f, and therefore the omega depend on the oscillation causing the wave. For example the frequency with which you moved your hand from side to side in the lab. Note that wavespeed is constant for the wave traveling in a medium, while the particle, or matter, velocity varies harmonically , as you would expect in a harmonic oscillation.

3) Nearly all of you got the first part of the very last question wrong ( item 8 at the end of the lab). See my notes so see the correct way to add them and BE MORE CAREFUL. Not everything is the easiest possible.

4) In order to answer a question, you must read it it. If they ask about phase answer about phase, not amplitude, not energy, not your favorite flavor. PHASE!!!! Waves can be represented as say y = A sin (omega t -kx) omega t -kx is th angle, the argument of sin , the PHASE, i.e what part of a cycle the wave is in.