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Homework Help: VERY BASIC Question on Waves

  1. Feb 6, 2010 #1
    Since speed = wavelength x frequency, I'd like to know what are the effects of increasing/decreasing the frequency? I know this sounds like a really basic question but I just can't understand it!
  2. jcsd
  3. Feb 6, 2010 #2


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    Homework Helper

    Hi MZET, welcome to PF.
    The relation " Since speed = wavelength x frequency" is true for a given medium.
    Frequency depends on the nature of the source. Speed and hence the wavelength depends on the nature of the medium.
    So for a given medium, as frequency increases, wavelength decreases.
  4. Feb 6, 2010 #3
    The speed of the wave is based on the properties of matter it travels through. I would recommend treating it as constant for a while.
    Let's have a theoretical wave with frequency of 1Hz and travelling at 1m/s. What it's wavelength. Now what happens if you double or half the frequency?

    If you understood that, you can send you wave through another matters where it travels with say 2 m/s or 0.5 m/s.

    If all above done, start travelling yourself. Go 0.5 m/s against and with the 1 m/s wave. How often will you encounter the same phase (e.g. top) of the wave? This is Doppler effect.
  5. Feb 6, 2010 #4
    Thanks for the answers guys! So does speed always decrease when frequency decreases?
  6. Feb 6, 2010 #5

    If you keep wavelength constant, which is about the only value you cannot in real world.
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