Before revision: In a region with no electrical conductivity, the expression simplifies to: For examples , in free space the intrinsic impedance is called the characteristic impedance of vacuum, denoted Z0, and Waves propagate through a medium with velocity , where is the frequency and is the wavelength of the electromagnetic waves.
After revision: In a region with no electrical conductivity, the expression simplifies to: For example , in free space the intrinsic impedance is called the characteristic impedance of vacuum, denoted Z0, and Waves propagate through a medium with velocity , where is the frequency and is the wavelength of the electromagnetic waves.