Say we have an AC voltage load that is connected to a transmitter dipole, radio antenna. The antenna has a length of $L =\frac{\lambda}{2}$ where $\lambda$ is the wavelength of the electromagnetic wave. Does this mean if we shorten the length of the antenna then we shorten the length of the wavelength? Theoretically, then couldn't you shorten the length of the dipole antenna enough to create microwaves and other types of higher-energy waves?
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If you shorten a half-wave dipole antenna but keep the excitation frequency the same then you will have a lousy radiator for most of the power from the antenna will be reflected back to the generator unless you also add some matching circuitry at the antenna input port. The operating wavelength of the radio wave in free space of the antenna does not change by the antenna. In fact, you can even have an infinitesimally short, so-called Hertzian dipole, that has almost the same radiation pattern as that of a half-wave dipole the essential difference between the two being that the latter has a reasonably wide bandwidth while the Hertzian dipole can only work at a single frequency, or more precisely on a very narrow bandwidth. Here are some more details.
