Does light of LED depend on current or voltage applied to it?
As an interview question the point might be just to get you to say that it isn't an &quot;either/or&quot; answer — of course the two are interrelated, and you can't have a current without a voltage!
However, consider the way an LED works: every time (well, hopefully most of the time) when an electron and a hole meet at the junction and recombine, a photon is emitted. The number of photons depends on the number of electrons, so the number of photons output per second depends on the charge passing through the device per second — that is, the current.