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Phase difference of original and reflected wave

  1. Aug 8, 2014 #1
    1. The problem statement, all variables and given/known data
    A radio station transmits a radio wave of 100Mhz. The radio wave is detected by a receiver via two diffrent paths , a direct path and refelcted path form a wall. The distance travelled by the radio wave for a direct path and refelcted path is 1500m and 1512 m respectively. Explain whether the intefrenece is constructive od destructive?


    2. Relevant equations



    3. The attempt at a solution
    refer to the sample ans attcahed, i don't undertstand why there's a phase change of 1/2 lambda when the wave is reflected?
     

    Attached Files:

  2. jcsd
  3. Aug 8, 2014 #2

    NascentOxygen

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    Staff: Mentor

    It is a characteristic of waves. Remember the wave travelling down a rope until it reaches the end anchored to a wall? When the wave hits the wall it returns along the rope, but inverted. Inversion of a sinewave = 180 degree shift

    The dark bands in a soap bubble are explained based on this inversion when reflecting off a more optically dense medium. When reflected off a less dense medium there is no inversion.
     
    Last edited: Aug 8, 2014
  4. Aug 8, 2014 #3
    Hello Nascent

    Does the phase change of reflected wave depend on the type of waves we are dealing with ?

    If instead of radio wave ,the question had sound wave reflecting from the wall , do you think it would also undergo phase change of 180 degrees ?

    Thanks
     
  5. Aug 8, 2014 #4
    hi, i have attched some of the standing wave pattern at difefrent time. for time T= t/4 , yes, the phase difference is 180 degree shift , but when t=0 . there's no phase difference for the incident and reflected waves.
     

    Attached Files:

  6. Aug 8, 2014 #5

    NascentOxygen

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    Staff: Mentor

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