Microwave Transmitter/Receiver

[JSapit]

Homework Statement

A microwave transmitter (T) and receiver (R) are set up side by side as shown.

https://chip.physics.purdue.edu/protected/Giambattista2EMimg/F25-5a.gif"

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.

https://chip.physics.purdue.edu/protected/Giambattista2EMimg/p25-11alt.gif"

(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 =

Homework Equations

F=1/T

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.

 

[skeptic2]

Why are there maxima and minima? What determines where they occur relative to x?

 

[JSapit]

Because of the constructive and destructive interference? And is is the phase shift?

 

[knyoung]

this is too hard for anyone on here to be able to figure out

 

[JSapit]

Anyone? I'm really lost :/

 

[skeptic2]

Because of the constructive and destructive interference? And is is the phase shift?

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.

 

[JSapit]

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.

 

[JSapit]

Okay...I got part two of the question, which was read straight off the graph...

 

[skeptic2]

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.

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?

 

[skeptic2]

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.

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.

 

[JSapit]

Ah hah! I got it! Thank you so much Skeptic!