Which physical quantity is measured in candelas?

Candelas are the unit of measurement for luminous intensity, which refers to the amount of light that is emitted in a particular direction by a light source. This unit quantifies how much visible light is emitted per unit solid angle and is a key component in the study of photometry.

In the context of photonics and lighting, measuring luminous intensity in candelas allows for a clear understanding of how intense a light source will appear to the human eye from a specific angle. This is particularly important for applications such as designing lighting in indoor and outdoor environments, where the perception of brightness can significantly affect usability and comfort.

The other options represent different physical quantities: electric current is measured in amperes, pressure in pascals, and temperature in kelvins. Each of these quantities has unique contexts and applications that are distinct from luminous intensity, emphasizing the specificity of the candela as a measure solely related to light and vision.