Luminous Intensity

 Define luminous intensity

Luminous intensity is a measure of the amount of light emitted in a particular direction per unit solid angle, as perceived by the human eye. It is defined as the luminous flux emitted per unit solid angle, with the unit of measurement being the candela (cd). The SI unit of luminous intensity is 'candela'.

To understand this definition, it is important to first define luminous flux. Luminous flux is the measure of the total amount of light energy emitted by a light source per second, measured in lumens (lm).

On the other hand, Solid angle, is a measure of the amount of space that a particular object or light source occupies in three-dimensional space, as viewed from a particular point. It is measured in steradians (sr).

The luminous intensity of a light source, therefore, is the amount of light energy emitted by the source in a particular direction, as perceived by an observer located at a particular point. For example, a flashlight with a high luminous intensity will emit more light in a particular direction, making it brighter to an observer located in that direction.

In summary, luminous intensity is a measure of the brightness of a light source in a particular direction, as perceived by the human eye. It is measured in candelas (cd), and is defined as the luminous flux emitted per unit solid angle.