Two antennas located at points A and B are broadcasting radio waves of frequency
ID: 2168861 • Letter: T
Question
Two antennas located at points A and B are broadcasting radio waves of frequency 95.0 MHz, perfectly in phase with each other. The two antennas are separated by a distance d= 9.30 m. An observer, P, is located on the x axis, a distance x= 67.0 m from antenna A, so that APB forms a right triangle with PB as hypotenuse. What is the phase difference between the waves arriving at P from antennas A and B?Now observer P walks along the x axis toward antenna A. What is P's distance from A when he first observes fully destructive interference between the two waves?
If observer P continues walking until he reaches antenna A, at how many places along the x axis (including the place you found in the previous problem) will he detect minima in the radio signal, due to destructive interference?
Explanation / Answer
You have already found ?L. If at the point P instructive interference takes place, then ?L = (2n + 1)*?/2. ........(1) Find the wavelength. Substitute the value of the wavelength in eq(1) and find n. If n is not an integer, at P there is no destructive interference. Select the nearest integer less than n. That is the first point of destructive interference with in 60 m.