We have a spot in our flat where there is little light. It is around 3 m (9 feet) away from the nearest window, the window goes to the east. In winter there is no direct light. We would still like to have a small plant in this corner near on the desk.
I'm looking into light bulbs that emit full spectrum light and found a couple. One model has 4 W of power draw, emits 300 lm of light which might give like 6 µmol/s of photons viable for photosynthesis. There are dedicated growth lights that emit like 100 µmol/s of photons.
It feels that just a single 4 W LED bulb would not make much of a difference, but it is also only thought as supplemental light and we don't want to set up a basement weed farm optimized for yield. Are there rules of thumb which would allow me to estimate whether such an LED light would make a difference for a plant?