Which two variables determine the primary frequency of any resonant cavity?

The primary frequency of any resonant cavity is fundamentally determined by its physical size and shape. In a resonant cavity, which can be found in various applications such as microwave cavities, antennas, or electronic circuits, the dimensions of the cavity dictate the wavelengths of the standing waves that can form within it.

Specifically, the size of the cavity determines the allowable modes of resonance. For instance, larger cavities support longer wavelengths, while smaller cavities favor higher frequencies due to the inverse relationship between frequency and wavelength. The shape of the cavity affects how these waves interact and can influence the distribution of the electric and magnetic fields, which directly impacts the resonance characteristics.

The other options involve factors that do not primarily govern the frequency of resonance in a cavity. Volume, while related to size, does not provide information about the specific modes; conductivity pertains more to losses than to frequency; length and width alone can be too simplistic since resonant behavior can depend intricately on three-dimensional shapes; and while material and temperature can affect operating conditions and performance, they do not fundamentally determine the resonance frequency directly.