A uniform plane wave traveling in air is incident on the plane boundary between air and another dielectric medium with $${\varepsilon _r} = 4$$. The reflection coefficient for the normal incidence, is

The depth of penetration of electromagnetic wave in a medium having conductivity $$\sigma $$ at a frequency of 1 KHz is 25 cm. The depth of penetration at a frequency of 4 KHz will be

If the electric field intensity is given by $$\mathrm E=\left(\mathrm x{\widehat{\mathrm u}}_\mathrm x\;+\mathrm y{\widehat{\mathrm u}}_\mathrm y+\mathrm z{\widehat{\mathrm u}}_\mathrm z\right)\;\mathrm{volt}/\mathrm m$$, the potential difference between X(2,0,0) and Y(1,2,3) is

The unit of $$\nabla\times\mathrm H$$ is