Answer
The television signals are polarized waves.
Work Step by Step
When the length of the rabbit ear is parallel to the direction of the incoming wave’s polarization, the electromagnetic wave can “shake” electrons effectively along the length of the ear.
Moreover, the rabbit-ear antennas are especially effective when each of the ears is one-quarter the wavelength of the incoming radiation (look up “dipole antenna” in your favorite Internet search engine), so adjusting the length and orientation of the ears can improve the reception considerably.
