A 100-kW radio station emits EM waves in all directions from an antenna on top of a mountain.What is the intensity of the signal at a distance of 10 km? A)8*10 ^- ⁵ W/m² B)8 *10 ^- ⁶ W/m² C)3 *10 ^- ³ W/m² D)0.8 W/m² E)2.5 *10 1^- ⁵ W/m²

Question

Quizplus · Accepted Answer

The intensity of an EM wave is given by:

I = P/(4πr^2)

where P is the power emitted by the source and r is the distance from the source.

In this case, P = 100 kW = 100,000 W and r = 10 km = 10,000 m.

Substituting these values in the equation, we get:

I = 100,000/(4π(10,000)^2)
  = 100,000/(4πx10^8)
  ≈ 8.0 x 10^-6 W/m^2

Therefore, the best choice is A.

A 100-KW Radio Station Emits EM Waves in All Directions