In a certain medium with $=$$0,$ $=4$$0$

Find

$($a$)$ the wave period T$,$ the attenuation coefficient $,$ the direction of propagation of the wave

$(5$ points$)$

$($b$)$ the wavelength and the speed of a wave $(5$ points$)$

$($c$)$ the electric field E$,$ using $=$

$=$

$+(5$ points$)$

$($d$)$ the phase difference between H and E $(5$ points