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Two antenas (two waves wih the same frequency)

  • Thread starter sameh1
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  • #1
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i really have some proplem with this 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= 60.0 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?

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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?

i calculated the phase difference between the two antenas but i didnt know how to to calculate the first time that i will recieve a destructive interfernce i think that it is when the phase difference is pi*(2m+1)

this is how i calculted the first quesion first i calculated the distance BP which is 60.716m
then i used the equation (phase difference=2*pi*delta L/ג ) delta L=BP-AP and ג=c/frequency which is given
 

Answers and Replies

  • #2
rl.bhat
Homework Helper
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You have already found ΔL. If at the point P instructive interference takes place, then
ΔL = (2n + 1)*λ/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.
 
  • #3
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hi
I tried to do what you told me but it does not help when i calculated n its negative and after i calculate n how can I calculate the distance AP I attached my try to solve the proplem
 

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  • #4
rl.bhat
Homework Helper
4,433
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ΔL = (2n + 1)*λ/2. ........(1)
Find the wavelength of the radio wave.
The first destructive interference will occur when ΔL = λ/2.
Now ΔL = sqrt(9.3^2 +x^2) - x...(2)
Put ΔL = λ/2 and solve for x.
Repeat the procedure for ΔL = 3λ/2, 5 λ/2......until x becomes negative.
 
  • #5
9
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Thanks a lot

I understand the proplem x is AP and I repeat the procedure to know how many time i have a destructive interfernce

if there is anything i can help with
 

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