Standing waves and a reflector

[map7s]

When a reflector is added to the previous setup, as shown in Figure 9 (page 201), a standing wave can be created. We are using a different detector in this case. Measuring the detector output as a function of distance along the goniometer (look it up!), we see that there are maxima and minima in the signal. Starting at one of the maxima, we find 3 additional maxima after moving the reflector a distance of 4.29 cm. Therefore, the frequency of the microwaves from this generator is ? GHz.

I first divided 0.0429 by 3 to find out the length of each wavelength and then used the equation c=wavelength*f to solve for f

(3E8)/(0.0429/3)=f

then I took that number and divided it by 1E9 to convert to GHz.

At first I thought that I messed up something about the wavelength and that maye it should be divided by four instead of three...so I tried that, and my answer was still wrong. :(

 

[map7s]

sorry...here is the attached picture

 

[andrevdh]

The positions where a maximum signal is detected corresponds to the antinodes of the standing wave. Midway in between these whe find the antinodes (minimum signal). What you need to clear up then is how the wavelength of the signal is related to the distance between the antinodes. One you have determined this relationship you know that 3 times this value is 4.29 cm (the distance four antinodes/maxima covers).