Question

A satellite orbiting Earth at an altitude of 450 km emits a radio signal that has a power level of 17 W when it reaches Earth. The signal is beamed in such a way that it covers an area of 7.0 m^2 on Earth’s surface. What power is received by a ground-based antenna if the surface area of the antenna is 400 mm^2

Answer 1

Given that,

Power = P = 17 W ; A1 = 7 m² ; A2 = 400 mm² = 0.0004 m²

Let P' be the required intensity.

We know that, intensity = power / area

I = 17 W / 7 = 2.43 W-m²

Power = Intensity x Area = 2.43 x 0.0004 = 0.000972 W

Hence, power recieved by the ground based antenna is = P' = 0.000972 Watts.