How is radiant energy typically measured?

Radiant energy is typically measured in joules, which is a unit of energy in the International System of Units (SI). The joule quantifies the amount of energy transferred when applying a force of one newton over a distance of one meter. In the context of radiant energy, it represents the energy carried by electromagnetic waves, including visible light, ultraviolet light, infrared radiation, and other forms of radiation.

While watts also relate to energy, they represent a measure of power, or the rate at which energy is used or transferred (1 watt = 1 joule per second). Therefore, while watts can be used in the context of discussing energy flow, they do not directly measure energy itself.

Lumens and candelas measure light as well, but they do so in terms of visible brightness and intensity, respectively. Lumens quantify the total perceived power of light emitted by a source, while candelas measure luminous intensity in a specific direction.

Understanding the distinction between these units is crucial, especially in fields like industrial hygiene where evaluating exposure to various forms of radiation is important for ensuring safety and compliance with standards.