Discuss the nature of the wave impedance at a distance of 1 metre from the following devices:
(i) A microwave oven operating at a frequency of 2.45 GHz.
(ii) A radio-frequency heat-sealer operating at 27 MHz.
(iii) The field coil of a 'deactivation pad' operating at 60 kHz. The pad is used in retail stores to demagnetise the tags attached to
merchandise to prevent theft.