'Lumen' is the unit of

Correct option is D

Lumen is the SI unit of luminous flux, which measures the total amount of visible light emitted by a source per unit of time.

Key points:
● Luminous flux quantifies the perceived power of light by the human eye.
● It differs from luminous intensity, which measures light in a specific direction (unit: candela).
● 1 lumen equals the amount of light emitted in a unit solid angle (steradian) by a uniform light source of 1 candela.
● Luminous flux considers the sensitivity of the human eye to different wavelengths of light.
● Lightbulbs and LEDs are rated in lumens to indicate their brightness.
● This metric is crucial for lighting design and energy efficiency.

Additional Information:

• Brightness is a subjective perception of light.
• Luminous intensity is measured in candela.
• Illuminance (unit: lux) measures light falling on a surface.