**radiant energy** is the energy of electromagnetic and gravitational radiation. As energy, its SI unit is the joule (J). The quantity of radiant energy may be calculated by integrating radiant flux (or power) with respect to time. The symbol *Q*_{e} is often used throughout literature to denote radiant energy (“e” for “energetic”, to avoid confusion with photometric quantities). In branches of physics other than radiometry, electromagnetic energy is referred to using *E* or *W*. The term is used particularly when electromagnetic radiation is emitted by a source into the surrounding environment. This radiation may be visible or invisible to the human eye.

Visible light such as sunlight carries radiant energy, which is used in solar power generation.

**Gravitational Radialtion**

**Gravitational waves** are disturbances in the curvature of spacetime, generated by accelerated masses, that propagate as waves outward from their source at the speed of light. Gravitational waves transport energy as **gravitational radiation**, a form of radiant energy similar to electromagnetic radiation.Newton’s law of universal gravitation, part of classical mechanics, does not provide for their existence, since that law is predicated on the assumption that physical interactions propagate instantaneously (at infinite speed) – showing one of the ways the methods of classical physics are unable to explain phenomena associated with relativity.

**Joule**

The **joule** ( symbol: **J**) is a derived unit of energy in the International System of Units. It is equal to the energy transferred to an object when a force of one newton acts on that object in the direction of the force’s motion through a distance of one metre(1 newton-metre or N⋅m). It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889).

**Ingrating radiant flux**

an **integral** assigns numbers to functions in a way that describes displacement, area, volume, and other concepts that arise by combining infinitesimal data. The process of finding integrals is called **integration**. Along with differentiation, integration is a fundamental, essential operation of calculus, and serves as a tool to solve problems in mathematics and physics involving the area of an arbitrary shape, the length of a curve, and the volume of a solid, among others. The integrals enumerated here are those termed **definite integrals**, which can be interpreted formally as the signed area of the region in the plane that is bounded by the graph of a given function between two points in the real line. Conventionally, areas above the horizontal axis of the plane are positive while areas below are negative. Integrals also refer to the concept of an antiderivate, a function whose derivative is the given function. In this case, they are called **indefinite integrals**. The fundamental theorem of calculus relates definite integrals with differentiation and provides a method to compute the definite integral of a function when its antiderivative is known

A definite integral of a function can be represented as the signed area of the region bounded by its graph.

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