Evanescent and Propagating Waves

Time domain simulation of a plane wave for different wavenumbers (k). At first the wavenumber is positive real number and keeps reducing down to 0. This constitutes the propagating region where the spatial wavelength (lambda) increases as the wavenumber (k) decreases. Then, wavenumber becomes negative imaginary and increases in magnitude. This region demonstrates the non-propagating or decaying properties of evanescent waves. In the evanescent region, the greater the magnitude of the wavenumber, the faster the wave decays.