Question

A dish antenna having a diameter of 22.0 m receives (at normal incidence) a radio signal from a distant source. The radio signal is a continuous sinusoidal wave with amplitude E_max = 0.800 µV/m. Assume the antenna absorbs all the radiation that falls on the dish. A dish antenna on top of a tall tower extending above the trees. The dish points upward and to the left. Three parallel wavy arrows come come downward and to the right toward the dish.

(a) What is the amplitude of the magnetic field in this wave? _______T

(b) What is the intensity of the radiation received by this antenna?_________ W/m2

(c) What is the power received by the antenna? _______W

(d) What force is exerted by the radio waves on the antenna?________N

Answer 1

given
d = 22 m
E_max = 0.8 micro V/m

= 0.8*10^-6 V/m

a) the amplitude of the magnetic field in this wave, B_max = E_max/c

= 0.8*10^-6/(3*10^8)

= 2.67*10^-15 T <<<<<<<<<<<<<---------------Answer

b) the intensity of the radiation received by this antenna, I = (1/2)*epsilon*c*E_max^2

= (1/2)*8.854*10^-12*3*10^8*(0.8*10^-6)^2

= 8.50*10^-16 W/m^2 <<<<<<<<<<<<<---------------Answer

c) the power received by the antenna, P = Intensity*Area of the antenna

= I*pi*d^2/4

= 8.50*10^-16*pi*22^2/4

= 3.23*10^-13 W <<<<<<<<<<<<<---------------Answer

d) radiation pressure, p = I/c

= 8.50*10^-16/(3*10^8)

= 2.83*10^-24 Pa

Force on the antenna, F = p*A

= 2.83*10^-24*pi*22^2/4

= 1.08*10^-21 N <<<<<<<<<<<<<---------------Answer