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The figure shows the popular dish antenna that receives digital TV signals from a satellite. The average intensity of the electromagnetic wave that carries a particular TV program is S̅ = 7.5 × 10-14 W/m2, and the circular aperture of the antenna has a radius of r = 15 cm. Concepts:
(i) How is the average power passing through the circular aperture of the antenna related to the average intensity of the TV signal?
(ii) How much energy does the antenna receive in a time t?
(iii) What is the average energy density, or average energy per unit volume, of the electromagnetic wave?
Calculations:
(a) Determine the electromagnetic energy delivered to the dish during a one-hour program.
(b) What is the average energy density of the electromagnetic wave? |
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