Radiant energy, as well as convective energy and conductive energy, is used for radiant heating.[17] It can be generated electrically by infrared lamps, or can be absorbed from sunlight and used to heat water. The heat energy is emitted from a warm element (floor, wall, overhead panel) and warms people and other objects in rooms rather than directly heating the air. The internal air temperature for radiant heated buildings may be lower than for a conventionally heated building to achieve the same level of body comfort (the perceived temperature is actually the same).

Various other methods and apparatus involving radiant energy have been devised.[18] All methods and apparatus using, generating, controlling or detecting radiant energy involve combinations of circuits which are closed or closable conducting paths through which, or along which, electric current can travel. In general, devices involving radiant energy is provided on the basis of either a specific use of the radiant energy or a specific type of radiant energy. Devices explicitly providing for subject matter involving radiant energy are:

Treatment and inspection

Separating and assorting

Medium of control

Medium of communication

Inspection is used to imply a source of radiant energy, and/or means to irradiate an object by said source and a detector responsive to radiation from the object to provide a signal representing some characteristic of the object. Various devices use material which when subjected to radiation for treatment or whose response to or effect on the radiation is used to indicate something about the material.

Photoelectric motor, US685957

Radiant energy falling on a insulated conductor connected to a capacitor: the capacitor charges electrically.Radiant energy detectors produce responses to incident radiant energy either as an increase or decrease in electric potential or current flow (Electric) or some other perceivable change (Nonelectric). The nonelectric change may be immediately perceived or may require development to be perceived, e.g., photographic changes. Since radiant energy is really just electromagnetic radiation under another name, it is the basis of a wide range of communication technologies using radiofrequency and microwave radiation. Radiant energy is observed by a detector, which is any material or device whose response to radiant energy is used to indicate the presence or amount of incident radiation. This is also called “Signalling Means”. Some devices are detectors used to sense light incident thereon and generate a signal representative of some aspect of the light such as intensity, phase, coherence, mode distribution, and interference pattern characteristics.

One of the earliest wireless telephones to be based on radiant energy was invented by Nikola Tesla. The device used transmitters and receivers whose resonances were tuned to the same frequency, allowing communication between them. In 1916, he recounted an experiment he had done in 1896.[19] He recalled that “Whenever I received the effects of a transmitter, one of the simplest ways [to detect the wireless transmissions] was to apply a magnetic field to currents generated in a conductor, and when I did so, the low frequency gave audible notes