# Wave Interference Question

1. Jul 25, 2010

### llamajuice

1. The problem statement, all variables and given/known data
The transmitting antenna for a radio station is 7.00km from your house. The frequency of the electromagnetic wave broadcast is 536kHz. The station builds a 2nd transmitting antenna that broadcasts an identical em wave in phase with the 1st one. The new antenna is 8.12km from your house. Show whether constructive or destructive interference occurs at your radio.

2. Relevant equations
v=f╗
v = c = 3 x 10^8 m/s

3. The attempt at a solution
So I found the wavelength: v/f 5.6x 10^2m, but I don't know how to tell when constructive or destructive interference occurs.

Last edited: Jul 25, 2010
2. Jul 25, 2010

### Swap

u r lacking some quantities. The question should also include where is the 2nd transmitting antenna. Let it be d
Then if u find that d=m(lambda) where m=0,1,2... then its a constructive interference.

3. Jul 25, 2010

### llamajuice

Oh I forgot to put that the new antenna is 8.12km from the house.
So if d = m(lambda) its constructive interference and if d just doesnt = m(lambda) then its destructive interference?

4. Jul 26, 2010

### Swap

no if d=(m+1/2)(lambda) then it will be destructive. also if both doesnt follow then it will be intermediate between two

5. Jul 26, 2010

### Swap

oh ok its a constructive.. as 1120/560 = 2.