4. 23. A center- fed electric dipole of length I is attached to a balanced lossless trans- mission line whose characteristic impedance is 50 ohms . Assuming the dipole Is resonant at the given length , find the input VSWR when ( a ) 1 = 1 / 4 ( b ) 1 = 1/2 ( c ) 1 = 31/ 4 ( d) 1 = 1