Originally posted by sebosfato
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As gyula said, lambda stands for wavelength. Lambda is the Greek letter L, apparantly for Length.
You may want to check these video's:
YouTube - Amplitude, Period, Frequency and Wavelength of Periodic Waves
YouTube - Sound - Vibration, Frequency, Wavelength
Beside "normal", traveling waves, you can have standing waves:
YouTube - Making standing waves
These consist of two waves traveling in opposit directions, such that they amplify one another. This is also known as resonance:
Standing Waves
Since a wave travels at a certain speed v, and has a certain frequency f, each single period of the vibration travels a specific distance lambda = v/f. So, with sound resonators, such as a pipe, you can pretty easily calculate the wave length of the sound wave that it produces when in resonance:
Resonances of open air columns
The lowest tone it can produce, is called "natural resonance". For a one-side closed cylinder containing air, the length of the cylinder is one quarter of the wave length, hence 1/4 lambda.
For straight wires, the same thing goes. For example, when you want to listen to a radio station transmitting at 100 MHz and you know the propagation speed equals 300.000 km/sec, you are talking about a wave length of 3 meters. Normally, you want your antenna to resonate in order to get the maximum voltage output, so you'd take 3 * 1/4 = 3/4 meters for an optimal antenna for 100 MHz reception, or 3 * 3/4 = 2 1/4 meters for a 3/4 lambda antenna.
The interesting thing is that if you take those standing waves a few steps further, you get most amazing patterns in fluids, etc:
YouTube - Cymatics - Bringing Matter To Life With Sound (Part 1 of 3)
While this is all being done using sound, you have the same kind of things with electro(magnetic) waves in the ether, only then you can't see them.





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