A lossless transmission line with Z0 = 75 Ω excited so as the wavelength of the line is 0.5 m. The line is said to be 0.23 m long and short circuited at load end. If the amplitude of the line voltage is 2.1 V at the midpoint, then the input voltage amplitude is ______.
1
0.52 V
2
4.2 V
3
2.1 V
4
0.74 V