Q: In this task you will be given an answer to a question. You need to generate a question. The answer given should be a correct answer for the generated question.
The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the total quantity of visible light emitted by a source. Luminous flux differs from power (radiant flux) in that radiant flux includes all electromagnetic waves emitted, while luminous flux is weighted according to a model (a 'luminosity function') of the human eye's sensitivity to various wavelengths. Lumens are related to lux in that one lux is one lumen per square meter.
A:
what is the difference between lux and lumens