NEET BIOLOGY

Detailed explanation-1: -What is light intensity measured in? The fundamental light intensity unit is the candela, nominally the light given off by one candle, or more precisely, “a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.”

Detailed explanation-2: -Lighting professionals use a light meter (also called an illuminance meter or lux meter) to measure the amount of light in a space/on a particular work surface. The light meter has a sensor that measures the light falling on it and provides the user with a measurable illuminance reading.

Detailed explanation-3: -The term intensity is used to describe the rate at which light spreads over a surface of a given area some distance from a source. The intensity varies with the distance from the source and the power of the source.

Detailed explanation-4: -Intensity is the power per unit area; it is a physical quantity. Brightness involves how the human visual system perceives light, and it is not a physical quantity.