# physics

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A 2.10 m diameter university communications satellite dish receives TV signals that have a maximum electric field strength (for one channel) of 7.90 µV/m.

(a) What is the intensity of this wave?
W/m2?
(b) What is the power received by the antenna?
W?
(c) If the orbiting satellite broadcasts uniformly over an area of 1.50 1013 m2 (a large fraction of North America), how much power does it radiate?
W?

• physics -

thats 10^13 m2

• physics -

(a) I =cε₀E²/2 =3•10⁸•8.85•10⁻¹²•(7.9•10⁻⁶)²/2=8.2•10⁻¹⁴W/m²
(b) P=I•A=I•πD²/4=8.2•10⁻¹⁴•π•2.1²/4=2.84•10⁻¹³ W
(c) P(total)=P•A(total) =2.84•10⁻¹³•1.5•10¹³=4.26 W

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