How Does Altitude Affect TV Signal Interference?

[simplicity12]

Homework Statement

Television and radio waves can reflect from nearby mountains or from airplanes. Such relfections can interfere with the direct signal from the station.
a. Determine what kind of interference will occur when 75-MHz television signals arrive at a receiver directly from a distant station and are also reflected from an airplane 134 m directly above the receiver. (Assume a wavelength/2 change in phase of the wave upon reflection.) Explain your reasoning.
b. Determine what kind of interference will occur if the plane is 42 m closer to the receiver. Explain your reasoning.

Homework Equations

v=f*wavelength
v=3.00 X 10^8 m/s

The Attempt at a Solution

I found the wavelength, which is 0.004 m. I don't know what to do next. Can someone help me please?

 

[eigenglue]

check your calculation of the wavelength again:

3.00 X 10^8 m/s = 75 X 10^6 s^-1 X ?m

Then, figure out whether the 134m to the plane is a whole number or wavelengths or not, and take into account the wavelength/2 change in phase.

 

[m2003]

a. The interference that will occur in this scenario is known as constructive interference. This is because the direct signal from the station and the reflected signal from the airplane will have a phase difference of 180 degrees. This means that the peaks of the waves will line up, resulting in a stronger signal at the receiver.

b. If the plane is 42 m closer to the receiver, the interference will change to destructive interference. This is because the reflected signal from the airplane will now have a phase difference of 90 degrees with the direct signal from the station. This means that the peaks of the waves will cancel out, resulting in a weaker signal at the receiver.

The reasoning behind this is based on the concept of path length difference. When the plane is 134 m directly above the receiver, the reflected signal travels an extra distance of 134 m compared to the direct signal, resulting in a phase difference of 180 degrees. When the plane is 42 m closer to the receiver, the reflected signal only travels an extra distance of 42 m, resulting in a phase difference of 90 degrees. This change in phase difference leads to a change in the type of interference observed.