Which of the following represents the base SI unit for luminous intensity?

The base SI unit for luminous intensity is the candela. This unit is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 10^12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. The candela is one of the seven base units in the International System of Units (SI), making it fundamental in the measurement of light intensity.

Luminous intensity specifically refers to the amount of light emitted by a source in a particular direction, enabling a more precise understanding of how light behaves in various applications, such as lighting design or when evaluating the performance of light sources. This is distinct from other units of light measurement, such as the lumen, which measures luminous flux, or lux, which measures illuminance, and the watt, which measures power. Each of these serves different purposes related to light but does not directly represent luminous intensity.