A uniform plane wave traveling in free space along the +$$z$$ direction and having its electric field along the$$ x$$-direction, is normally incident on a thick brass sheet, infinite in extent (along the $$x$$-and $$y$$-directions). The electric field intensity of the wave is given by $$${E_x} = 1225\,\cos \,\left( {5.89 \times {{10}^{10}}t - \beta z} \right)\,\,\,\,V/m$$$.

Calculate the power per square metre that causes heating of the brass sheet, taking $${ \in _r} = 1,\,\,\,{\mu _r} = 1$$ and $$\sigma = 1.649 \times {10^7}\,\,\,\,\,$$ mhos/metre for brass.

Two dissimilar antennas having their maximum directivities equal

The beam width-between-first-null of a uniform linear array of N equally-spaced (element spacing = d) equally-excited antennas is determined by

Elements of a linear array of three equally spaced (element spacing $$0.5\lambda $$ ) vertical mast radiators are excited as given in Fig. For the horizontal plane radiation pattern of the array determine the direction of the major lobe (main lobe or principal lobe) and calculate its half-power-beam-width in degrees.