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**[SOLVED] Interference of waves - 2 point source Question**

## Homework Statement

Two towers of a radio station are 400 m apart along an east-west line. The towers act essentially as point sources, radiating in phase at a frequency of 1.00 x 10^6 Hz.

a) In what directions is the intensity of the radio signal at a maximum for listeners 20 km north of the transmitter (but not necessarily directly north of it)?

b) In which directions would you find the intensity at a minimum, north of the transmitter, if the towers were to start transmitting in opposite phase?

## Homework Equations

__(n-1/2)lamda__= sin theta

d

where n - the number of nodes

theta - the angle between nodes

d - distance between 2 point sources

velocity= lamda x frequency

## The Attempt at a Solution

I thought that I want to figure out the angle between the central max, and the first node - where the radio signal would be at a minimum (due to destructive interference) and then divide it by 2 to get the angle at the maximum (constructive interference).

lamda=

__3.00 x 10^8 m/s__= 300 m

1.00 x 10 ^ 6 Hz

__( 300m)__(1-1/2)= sin theta

400 m

theta = 22 degrees / 2

= 11 degrees

My answer was N 11 E or N 11 W, whereas the real answer should be N 49 E or N 49 W.

Help please!

Thanks!

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