Why is the physical length of a coaxial cable shorter than its electrical length?

The electrical length of a cable is based on the physical wavelength of the RF signal traveling through it. Because the dielectric material inside a coaxial cable slows down the RF energy compared to its speed in air or a vacuum, the signal's physical wavelength inside the cable is compressed. As a result, a physical piece of cable that is cut to match one full "electrical wavelength" will actually be shorter than a full wavelength measured in free space. To find the required physical length, you must multiply the free-space wavelength by the cable's velocity factor. The incorrect options introduce concepts like surge impedance, characteristic impedance, and skin effect. While these are real electrical properties, they govern power transfer and resistance, not the propagation speed or the resulting physical-to-electrical length ratio.