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Is frequency vibration

  1. Dec 20, 2012 #1
    When presented with different phenomenons it can be hard to imagine the relationship between each other. Although I am able to work out different problems involving it and sometimes provide good arguments around it I haven't yet gained enough confidence on how to imagine frequency.

    Is frequency vibration? Considering it in many different applications such as radio/electromagnetic frequency, de Broglie's wavelength, wave particle duality etc.

    Thanks.
     
  2. jcsd
  3. Dec 20, 2012 #2

    russ_watters

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    Staff: Mentor

    Frequency can be used to describe anything that happens at a regular interval.
     
  4. Dec 20, 2012 #3
    Yes and no. As Russ said frequency applies to a wider range of phenomena that are not vibratory, but it also applies to vibratory phenomena.

    So for example

    If I hold one end of my ruler down on the desk and twang the other end the ruler executes vibration up and down at a regular frequency.

    However I have a birthday ( I will say where to send presents) that has a frequency of once a year!

    :rofl:

    Phenomena that occur with a regular frequency are referred to as cyclic. The term is often associated with rotation. So a shaft can rotate at a frequency of 100 rpm, but most engineers would try to avoid any vibration.

    Does this help?
     
  5. Dec 20, 2012 #4
    Yes it does. Thanks.

    So what cyclic behaviour would electromagnetic frequency exhibit. I don't think it would be clever to imagine the photon moving up and down. And how would you imagine the frequency of a moving object such as a ball. Is it the small change of displacement along its path (vibration)? If that is the case then the ball may be vibrating in lots of different directions.

    It has been helpful by using cyclic above, because it has given me a general view of frequency. But when you use the idea in connection with different phenomena it does tend to raise other ideas. In most phenomena they relate frequency with other variables such as mass, wavelength, momentum etc.
     
  6. Dec 20, 2012 #5
    How is this cyclic or occurring at regular intervals?

    The phenomenon has to occur several (many?) times and the interval (usually time) between each occurrence has to be the same, ie regular.

    The kilometre markers on a motorway are spaced at regular spatial intervals (of 1 kilometre) or a spatial frequency of 1 kilometre.

    If you drive at a constant speed you will pass them at a temporal frequency of 1/speed.
     
  7. Dec 20, 2012 #6
    YES!!! I understand now. That was a good example. I understand that well now (ie: frequency is per application being characterised in it is not entire restricted).

    So in terms of electromagnetic waves and de Broglie's wavelength formula (Quantum phenomena). What characteristic cyclic change are they referring to when they use frequency.
     
  8. Dec 20, 2012 #7
    The question of what is vibrating for electromagnetic waves such as X rays, light etc is difficult.
    The simplest way to look at it is to say that there are linked electric and magnetic fields that vary in intensity a regular manner (like the kilometre posts) in both space and time.
    So a frequency defining this regular variation can be defined by the interval between repetitions of the variation.

    I try to think of a pattern that repeats every so many microseconds or nanoseconds.

    That way you avoid the thorny question of vibration and therefore what vibrates.

    The question of quantum vibration is even more abstract and requires the acceptance of some pretty abstract ideas.
     
  9. Dec 20, 2012 #8

    jtbell

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    Staff: Mentor

    When an electromagnetic wave passes a charged particle, the particle experiences an electric force that oscillates in a cyclic fashion: first upwards, then downwards, then upwards, etc. Loosely speaking, this is how radio-receiving antennas work: the oscillating electric fields in the radio (electromagnetic) waves cause electrons in the antenna to oscillate.
     
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