(D Ay=ey vheB=O(V米 y(x,t)=yo(e eye yo()=/e = −  = = =  = = −  − x i p dl iEt x Ne E x t x e when B x H E A c q H P             / 0 0 0 2 2 / 0 2 ( ) 2 ( , ) ( ) 0 ( ) ) ˆ ( 2 1         