# Homework Help: Theory question on Waves

1. May 4, 2007

### simplicity12

1. The problem statement, all variables and given/known data
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.

2. Relevant equations
v=f*wavelength
v=3.00 X 10^8 m/s

3. 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?

2. May 5, 2007

### 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.