Calculate the range of EM waves which can be transmitted by the antenna of height 20 meter. given the radius of the earth=6400km

Dear Student ,
Here in this case from the given data we can write that the range of the EM waves which can be transmitted is ,

$d=\sqrt{2h{R}_e}=\sqrt{2\times 20\times 6400\times 1000}=16000 m=16 km$
Regards