"n" in standing waves

[mcgill2012]

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is this correct?

for standing waves in a string, n is equal to the number of antinodes. lambda = 2L/n

for standing waves in an open tube, n is equal to the number of nodes. lambda = 2L/n

for standing waves in a closed tube, n is equal to the number of nodes. lambda = 4L/n

im having trouble understanding this conceptually though.. any advice?

 

[dextor2003]

i hated this topic with a passion cuz i missed this lecture in my physics class and never understood it because of that...until 3 weeks ago.

what i did was just study the actual pictures they give you on the mcatreview website. i eventually just engrained them in my head until it became second nature. if you can visualize how much of the wavelength you have in whatever situation (like open pipe on both ends, closed pipe on both ends, etc), then you can visually see the relationship between the length of the pipe and the wavelength. and the equations actually start to make intuitive sense

hope that helps

 

[methylethyl88]

for standing waves in a closed tube, remember that n = 1, 3, 5 because the phase of the pulse is inverted with each full trip

 

[VicodinMan]

Standing waves are usually produced by two waves that interfere with each other. However, one of the two waves is somewhat "ahead" of the other. So what you have is some parts of the wave being reinforced while other parts cancel out.

is this correct?

for standing waves in a string, n is equal to the number of antinodes. lambda = 2L/n

Yes. A string is usually fixed on both ends, which limits the number of possible nodes. That's why it's 2L/n and not 4L/n.

for standing waves in an open tube, n is equal to the number of nodes. lambda = 2L/n

for standing waves in a closed tube, n is equal to the number of nodes. lambda = 4L/n

Also read this: http://cnx.org/content/m12589/latest/

 

[mcgill2012]

thanks for the great information 🙂