Question

Two radio antennas A and B radiate in phase. Antenna B is a distance of 120 m to the right of antenna A. Consider point Q along the extension of the line connecting the antennas, a horizontal distance of 40.0 m to the right of antenna B. The frequency, and hence the wavelength, of the emitted waves can be varied. What is the longest wavelength for which there will be destructive interference at point Q?

Answer 1

Answer:

240 m

120 m

Explanation:

d = Path difference = 120 m

For destructive interference

Path difference

$d=\dfrac{\lambda}{2}\\\Rightarrow \lambda=2d\\\Rightarrow \lambda=2\times 120\\\Rightarrow \lambda=240\ m$

The longest wavelength is 240 m

For constructive interference

$d=\lambda\\\Rightarrow 120\ m=\lambda$

The longest wavelength is 120 m