Electromagnetic wave is half wave, i.e. perpendicular to the direction of oscillation and propagation, when the voltage is maximum in the antenna during the electromagnetic wave radiation, the current is zero, and when the voltage is zero, the current is maximum. The electric field for voltage and the magnetic field for current are perpendicular to each other. Shown above are transverse electromagnetic waves. Basically the antenna is placed in our surrounding atmosphere. The atmosphere is here referred to as vacuum. In vacuum, electromagnetic waves travel at speeds close to the speed of light.