The antenna radiates electro magnetic waves from a height h_t ,Then the range

If a source is transmitting electro magnetic waves of frequency 8.196 xx 10^(6) Hz, then the wavelength of the electromagnetic waves transmitted from the source will be

A body projected horizontally with a velocity v from a height h has a range R .With what velocity a body is to be projected horizontally from a height h//2 to have the same range ?

Advantage of HF transmission is ( A ) that the length of antenna is small ( B ) that the antenna can be mounted at larger heights ( C ) that the power radiated is more for a given length of antenna

If the sum of the heights of transmitting and receiving antennas in line of sight of communication is fixed at h, show that the range is maximum when the two antennas have a height h//2 each.