A transmitting antenna of height 20 m and the receiving antenna of height h are separated by a distance of 40km for satisfactory communication in line of sight mode. Then the value of h is

Options

A. 40m
B. 45m
C. 30m
D. 25m

Answer

B

Explanation

`d_(M)=sqrt(2Rh_(R))+sqrt(2Rh_(T))`
where `h_(R)` and `h_(T)` are the heights of receiving and transmitting antenna and r is the radius of the earth.
`40xx10^(3)=sqrt(2xx6400xx10^(3)xxh)+sqrt(2xx6400xx10^(3)xx20)`
`40xx10^(3)=sqrt(2xx6400xx10^(3)xxh)+16xx10^(3)`
`h=([(40-16)xx10^(3)]^(2))/(2xx6.4xx10^(6))=45m`