Which of the following is dealt with point sources and measured in candelas?

The concept of luminous intensity is explicitly defined as the amount of light that is emitted from a point source in a particular direction, measured in candelas (cd). This unit quantifies the power emitted by a light source in the direction of the observer and is foundational in understanding how light behaves in various scenarios, such as in lighting design and photometry.

Candelas represent the intensity of light sources, and this concept is critical in applications like designing lighting systems or analyzing visual performance. Luminance, on the other hand, refers to the amount of light that is reflected off a surface or emitted by a surface per unit area, measured in candelas per square meter. Illuminance measures the amount of light that falls on a surface, expressed in lux or foot-candles, and does not focus on emission from a point source. Brightness is a subjective perception of visual intensity and does not have a standardized measurement unit like candelas.

This distinction emphasizes why luminous intensity, specifically quantifying point sources, is accurately measured in candelas. Understanding these metrics is crucial for professionals involved in fields that require precise light measurements and assessments.