Question

What is the SI Unit of brightness/illuminance

• A. Candella
• B. Luminance
• C. Lumen
• D. Lux

Answer 1

The Correct Option is D

The SI unit of brightness or illuminance is known as Lux. Illuminance is a measure of how much luminous flux is spread over a given area. One lux is equal to one lumen per square meter. In other words, it quantifies the amount of light that hits a surface or is visible in a particular area.

Let's break down the options provided:

• Candella: This is a unit of luminous intensity, which measures the power emitted by a light source in a particular direction. It is not used to measure illuminance.
• Luminance: This refers to the intensity of light that is emitted or reflected from a surface in a specific direction per unit area. It is measured in units like candela per square meter, but it is distinct from illuminance.
• Lumen: This is a measure of the total amount of visible light emitted by a source. It is associated with luminous flux, not directly with illuminance.
• Lux: As stated above, this is the correct unit for measuring brightness or illuminance, capturing the amount of light that falls on a given surface.