Wave Interference at Radio Station Antennas

[llamajuice]

Homework Statement

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.

Homework Equations

v=f╗
v = c = 3 x 10^8 m/s

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.

 

[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.

 

[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 doesn't = m(lambda) then its destructive interference?

 

[Swap]

no if d=(m+1/2)(lambda) then it will be destructive. also if both doesn't follow then it will be intermediate between two

 

[Swap]

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