1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Microwave Transmitter/Receiver

  1. Mar 27, 2009 #1
    1. The problem statement, all variables and given/known data
    A microwave transmitter (T) and receiver (R) are set up side by side as shown.


    Two flat metal plates (M) that are good reflectors for microwaves face the transmitter and receiver, several meters away. The beam from the transmitter is broad enough to reflect from both metal plates. As the lower plate is slowly moved to the right, the microwave power at the receiver is a function of x is shown in the graph below, in which each interval along the horizontal axis equals 1.0 cm.


    (a) What is the wavelength of the electromagnetic radiation?

    (b) What is the ratio of the amplitudes of the electromagnetic radiation entering the detector for the two maxima shown?

    first / second =

    2. Relevant equations


    3. The attempt at a solution

    I don't know where to start. I know that the frequency is 1/T, but they don't give us time. I'm not sure what to do with the increasing increments on the graph.
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
  3. Mar 27, 2009 #2
    Why are there maxima and minima? What determines where they occur relative to x?
  4. Mar 27, 2009 #3
    Because of the constructive and destructive interference? And is is the phase shift?
  5. Mar 27, 2009 #4
    this is too hard for anyone on here to be able to figure out
  6. Mar 27, 2009 #5
    Anyone? I'm really lost :/
  7. Mar 27, 2009 #6
    Yes and Yes. Now what is the distance on the graph from maximum to maximum in centimeters? How many wavelengths or fractions of a wavelength would the plate have to move to go from constructive to destructive to constructive interference? Finally you need to relate the distance from maximum to maximum in centimeters to the distance in wavelengths the plate would have to move to go from constructive interference to constructive interference.
  8. Mar 27, 2009 #7
    Would the wavelength just be 3 cm, read straight from the graph? I tried that, but it didn't work. Sorry, but I'm a little confused with your explanation. Would the apparatus just move 1cm to get to destructive interference, and then another 1cm to get to constructive interference? I'm not quite sure how to read the graph.
  9. Mar 27, 2009 #8
    Okay...I got part two of the question, which was read straight off the graph...
  10. Mar 27, 2009 #9
    No, the distance between the two maxima is 3 cm but don't forget the the microwaves have to travel that distance twice, once from the transmitter to the plate and again from the plate to the receiver. So what would the wavelength have to be to have two maxima at 3 cm apart?
  11. Mar 27, 2009 #10
    So if each vertical line is 1 cm then the first maximum is at 1.5 cm. The minimum is at 3 cm and as you pointed out the two maxima are 3 cm apart so the second one is at 4.5 cm.
  12. Mar 28, 2009 #11
    Ah hah! I got it! Thank you so much Skeptic!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook