Definition - What does Radiant Energy mean?
Radiant energy is the energy carried by electromagnetic and gravitational radiation, although it is mostly used with reference to the former. In analyses of electromagnetic radiation (EM) that describes radiation as being comprised of photons, radiant energy is the energy carried by the photons. In analyses that describe EM radiation as being comprised of waves, radiant energy is the energy of the waves’ oscillating magnetic and electric fields.
As with all forms of energy, the unit used to quantify radiant energy is the joule (J). The term “radiant energy” is also sometimes used to refer to EM radiation in generic terms, without respect to the specific amount of energy associated with the radiation.
Safeopedia explains Radiant Energy
Radiant energy is chiefly relevant to occupational health and safety issues involving heat and light. For example, the temperature experienced by humans (called apparent temperature) is heavily influenced by sources of visible and infrared radiation (e.g., sunlight, fire). Threshold limit values for exposure to environmental heat are described with reference to “wet-bulb globe temperature,” a measurement of apparent temperature that accounts for the role radiant energy plays in producing environmental heat.
The non-thermal contexts in which radiant energy plays a significant role are primarily those related to the potential harmful exposure to visible light, including exposure to lasers. Any significant length of optical exposure to the high levels of visible radiation emitted by activities such as welding requires the use of mandatory PPE eyewear to prevent eye damage. Industrial lasers also emit a higher-energy form of radiation, and even short lengths of exposure may be sufficient to injure workers if appropriate eye protection is not worn.
Ionizing radiation, such as gamma radiation, can also be described as radiant energy. This form of radiation can cause cancer and other illnesses. However, measurements related to ionizing radiation are not usually described in terms of radiant energy. They are instead described in terms of subject-specific units such as becquerels (amount of activity), coulombs/kilogram (amount of exposure), grays (absorbed dose), and sieverts (dose equivalent). These situation-specific forms of measurement are more useful for understanding ionization hazards than is the more generic concept of radiant energy.