Question

A radio station transmits isotropically (that is to say in all directions) electromagnetic radiation at the frequency of 98.6 MHz. At a certain distance from the radial station the intensity of the wave is I = 0.291 W / m^2.

a) What will be the intensity of the wave at a quarter of the distance from the radio station?
 

b) What is the wavelength of the transmitted signal?

If the antenna power is 8 MW.
c) At what distance from the source will the wave intensity be 0.146 W / m^2?
 

d) What is the absorption pressure exerted by the wave at that distance?
 
e) What is the effective electric field (rms) exerted by the wave at that distance?
 

Answer 1

1) Intensity is inversely proportional to distance from antena

so intensity at quarterly distance from radio station

2) wavelength of transmitted signal

c) so Power = 8MW

so at distance r intensity

so we get

d) reflaction pressure

e) so we know

so,

and