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Not understanding some parts of wave refraction
On Apr 5, 7:36 am, "MRW" wrote:
I am skimming thru the Propagation chapter of the ARRL handbook, and I am having a difficult time understanding the shortening of wavelength and the retainment of frequency. They have an equation showing that wave velocity is: c = f*w (c = m/s, f = frequency, w = wavelength). It also states that during refraction "the wavelength is simultaneously shortened, but the wave frequency (number of crests that pass a certain point in a given unit of time) remains constant." I don't understand. If the wavelength is shortened, then shouldn't the frequency increase instead of remaining constant? Refraction occurs when an EM wave, having frequency f and wavelength w enters a medium in which the speed of propagation (speed of light) is different than vacuum. A medium with an index of refraction greater than one produces a speed of light which is slower than in vacuum (index of refraction is simply the ratio of vacuum speed to speed in that medium). This changes the proportionality between frequency and wavelength. Since w = c / f, the slower speed at a given frequency will now have a correspondingly shorter wavelength. And, as f = c / w, the slower speed at a given wavelength will now have a correspondingly lower frequency. I hope that makes sense. 73, Jim AC6XG |
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