Question

‘Lumen’ is the unit of which of the following?
1. Luminous Intensity
2. Luminous Flux
3. Magnetic Flux
4. None of these

Answer 1

Correct Answer - Option 2 : Luminous Flux

The Correct Answer is Luminous Flux.

• Luminous Flux is energy per unit time that is radiated from a source over visible wavelengths.
• More specifically, it is energy radiated over wavelengths sensitive to the human eye, from about 330 nm to 780 nm. 
• Thus, luminous flux is a weighted average of the Radiant Flux in the visible spectrum. 

• Luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye.
• The SI unit of luminous intensity is the candela, an SI base unit.
• In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface.
• The SI unit of magnetic flux is the weber and the CGS unit is the maxwell.