Question

A radio station operating at a frequency 100 KHz has two vertical dipole antennas spaced 400 m apart
oscillating in phase. In which directions is the intensity greatest?

• A. $0,\pm {30}^0,\pm {90}^0$
• B. $0,\pm {30}^0,\pm {60}^0$
• C. $0,\pm {45}^0,\pm {90}^0$
• D. $\pm {30}^0,\pm {60}^0,\pm {90}^0$

Answer 1

The correct option is A $0,\pm {30}^0,\pm {90}^0$

$\lambda =\frac{c}{f}=\frac{3\times {10}^8}{1.5\times {10}^6}=200m,sin\theta =\frac{n\left(200\right)}{400}=\frac{n}{2},i.e.,\theta =0,\pm {30}^0,+\pm {90}^0.$