例 5-4 设区域 (xlt 0) 是理想的空气介质,区域 (zgt 0) 媒质参数为 _(2)=5,-|||-(mu )_(2)=20 -_(2)=0 。在区域I中的电场强度为-|||-_(1)=e[ 60cos (omega t-(beta )_(1)t)+20cos (omega t+(beta )_(1))] (V/m)-|||-区域Ⅱ中的电场强度为-|||-_(2)=(e)_(1)[ Acos (omega t-(beta )_(2))] (V/m)-|||-(1)求常数A。-|||-(2)当 omega =15times (10)^8 时,求相移常数β1和β2-|||-(3)当 omega =15times (10)^8 时,求磁场强度H1和H2