2、介质变化型 2n22= 2x(l-11)E R 2ml,, 尺 2rl 8 2 C=C1+C2= R R C=A+BL2、介质变化型 1 2 1 1 2 1 2 1 1 1 2 2 1 2 2 ln 2 ( ) ln 2 ln 2 ln 2 ( ) ln 2 C A Bl r R l r R l C C C r R l C r R l l r R l C = + − = + = + = − = =           