A local radio station transmits radio waves uniformly in all directions with a total power of 7.50 × 10⁴ W. What is the intensity of these waves when they reach a receiving antenna located 20.0 km from the transmitting antenna? A)1.49 × 10^-⁵ W/m² B)5.96 × 10^-⁵ W/m² C)3.73 × 10^-⁶ W/m² D)1.17 × 10^-⁷ W/m² E)5.60 × 10^-⁸ W/m²

Question

Quizplus · Accepted Answer

The intensity of a wave is given by the equation I = P/4πr^2, where P is the power of the wave and r is the distance from the source of the wave. In this problem, the power of the wave is 7.50 × 10^4 W and the distance from the source of the wave is 20.0 km = 20,000 m. Plugging these values into the equation, we get I = (7.50 × 10^4 W)/4π(20,000 m)^2 = 1.49 × 10^-5 W/m^2.

A Local Radio Station Transmits Radio Waves Uniformly in All