I want to know the answer to the following question:
In how many ways can one define luminous efficacy of a light source?
All the background I'm provided with is that "Not all wavelengths of visible electromagnetic energy are equally effective at stimulating the human eye; the luminous efficacy of radiant energy (LER) is a measure of how well the distribution of energy matches the perception of the eye.". Is that enough to answer the question?
Answer: no