Dielectric heating at low frequencies, as a near-field effect, requires a distance from electromagnetic radiator to absorber of less than ⁠ 1 / 2 π ⁠ ≈ ⁠ 1 / 6 ⁠ of a wavelength. It is thus a contact process or near-contact process, since it usually sandwiches the material to be heated (usually a non-metal) between metal plates taking the place of the dielectric in what is effectively a very large capacitor. However, actual electrical contact is not necessary for heating a dielectric inside a capacitor, as the electric fields that form inside a capacitor subjected to a voltage do not require electrical contact of the capacitor plates with the (non-conducting) dielectric material between the plates. Because lower frequency electrical fields penetrate non-conductive materials far more deeply than do microwaves, heating pockets of water and organisms deep inside dry materials like wood, it can be used to rapidly heat and prepare many non-electrically conducting food and agricultural items, so long as they fit between the capacitor plates.