Radio station KBOB broadcasts at a frequency of 85.7 MHz on your ...

[crobinson2013]

Radio station KBOB broadcasts at a frequency of 85.7 MHz on your dial using radio waves that travel at 3.00  108 m/s.
 
  Since most of the station's audience is due south of the transmitter, the managers of KBOB don't want to waste any energy broadcasting to the east and west. They decide to build two towers, transmitting in phase at exactly the same frequency, aligned on an east-west axis. For engineering reasons, the two towers must be AT LEAST 10.0 m apart. What is the shortest distance between the towers that will eliminate all broadcast power to the east and west?

Question 2

Two stereo speakers mounted 4.52 m apart on a wall emit identical in-phase sound waves. You are standing at the opposite wall of the room at a point directly between the two speakers.
 
  You walk 2.11 m parallel to the wall, to a location where you first notice that the sound intensity drops to zero. If the wall along which you are walking is 10.7 m from the wall with the speakers, what is the wavelength of the sound waves? CAREFUL The distance to the wall is NOT much greater than the distance between the speakers.
  A) 1.7 m
  B) 2.1 m
  C) 2.6 m
  D) 2.9 m

[mrphibs]

Answer to Question 1

12.3 m

Answer to Question 2

A

[crobinson2013]

Excellent

[jackie]

Gracias!